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I would suggest don't quote me on this as the phrase you seek. The literal meaning of course, is to ask that responsibility for a statement not be ascribed to the person making it, such as an insider leaking private information to a journalist. It is a request that the statement be paraphrased, perhaps, but particularly that the name of the person making it not be indicated.

From there, don't quote me has taken on a sense of I believe what I am saying is true, but I may be inaccurate in particular details or I am presenting gossip or conjecture as truth, but I do not have factual information to support it, and from there it has perhaps become an even more generic mechanism for distancing a speaker from the statement. It is often used jokingly in this way, to make a humorous impression, draw an outrageous analogy, make an insulting comment, and so on but quickly indicate to the reader or listener that the speaker is not making a serious argument.

Literal sense of "please do not ascribe a quote to me":

"Holy shit!" exclaimed one Republican on the Armed Services Committee when a reporter shared the news about Mattis. "Don’t quote me on that." (The Hill)

Sense of I am making a statement but understand my information is incomplete or inaccurate:

The West Virginia/Syracuse line had a lot of movement around gametime, so don't quote me on who ended up being the favorite in that game, but I'm fairly certain either every single or almost every single Big 12 team was an underdog for their bowl game. (Dallas Morning News)

Examples of facetious usage:

Roughly speaking, there are 1,000,000 yoga teachers in London alone and only 100,000 studios (don't quote me on those statistics). (The Daily Telegraph)

We in the West scoff our Pop Tarts (surely descended from the Cornish pasty? Don’t quote me on that!)… (The Independent)

The identical expression exists in English, but it deals with specificity or the ease of categorization rather than truth or accuracy:

Unfortunately, this guess can't be nailed down without lots of additional research. — “Something is flashing brightly in deep space and scientists have no idea why,” BGR.com, 4 Apr. 2018.

But on Tuesday, he said “I can't be nailed down today on the specifics of what I might or might not run for.” — “Howard Schultz on presidential speculation: ‘Let's see what happens,’” CNBC.com, 5 June 2018.

The answer isn't that simple, it can't be nailed down to just one particular issue or one reason. — “This is Why Farmland Prices Really Won't Come Down,” DreamDirt blog, 14 Jan. 2018.

There are several equivalents in English for introducing a rough guess/estimate or any statement whose accuracy a speaker is unable to vouch for. Perhaps the most common one is “Don’t hold me to it…”

We have about a half a million people, I think. Don't hold me to it. — Culture and countries, Tulsa, LingQ

“Where is that big-headed husband of yours?” Tonee asked Keylona. “Don't hold me to it, but he said he had a lot of work he had to get done around the office today.” — Chillee Willee, Say It Isn’t So, 2010.

“Can’t say for certain, and I sure as hell couldn’t testify to it, you know, under oath or anything like that.”

“I doubt you'll ever have to.”

“All right, long as you don’t hold me to it. I’d say it started in the parlor on the ground floor. Somebody put a candle too close to a curtain in the front window, the curtain caught fire, and the whole place went up. I got no proof of that, of course, but I did find the brass candlestick.” — Christopher C. Gibbs, Rest Her Soul: A James Buckner Novel, 2012.

The firefighter in this novel manages to hedge his guess about what started a fire with three expressions:

Can’t be certain

I couldn’t testify to it (more common: couldn’t swear to it)

Don’t hold me to it

Take this with a grain of salt

(With) a grain of salt", (or "a pinch of salt") is an idiom of the
English language, which means to view something with scepticism or not
to interpret something literally

Source: wikipedia

Another definition and an example from theidioms.com

accept, but with some reservations or skepticism

Example:

I’ll take anything he says with a grain of salt. He has a habit of
exaggerating things.

"...but no guarantees"

Literally this means that the giver has no responsibility to the receiver if the "product" (in this case, the advice/assertion) proves to be faulty.

Caveat emptor

This is a far less common phrase, but it would usually be understood by educated people. It has a very similar meaning to the above. It basically means "buyer beware". In my experience this is far more frequently used in writing than spoken.

This is not the most direct translation, but as an idiom,

"your mileage may vary"

is often used to indicate that the preceding information might not prove to be completely accurate, perhaps because your own circumstances differ from those of the person imparting it.

Other answers are attempting to give English versions of the German idiom but if I was giving information which I was unsure of there are more direct, non-idiomatic, ways of doing this.

"As far as I know..."
eg: As far as I know he was only here for three weeks.

"It is my understanding that..."
eg: It's my understanding that there will be free food.

Both of those are very easily and naturally followed by some of the idioms given in other answers.
eg: As far as I know the pay is $50 an hour, but don't hold me to that.

"All care, no responsibility".

While this can be a formal disclaimer it is as likely to be a somewhat lighthearted response and quite a good fit to what you asked about.

"I am no a lawyer, but ..." / IANAL, ...:
= I believe this advice is good BUT I am not legally qualified to give it and it's not my fault if it's wrong.
The "IANAL" is seen only in written form.

Caveat Emptor.
"Let the buyer beware". While this probably originated as a formal warning it's usually now seen more in light hearted or informal form.

Your mileage may vary / YMMV.

I tend to use this :-).

Based on US mpg claims for motor vehicles. It's noting that even though the test car achieved these results there is no certainty that YOUR car will.
Now used in many situations to indicate what may be expected, with the warning that actual experiences may differ.

YMMV largely used in written situations but would be understandable if used verbally in some situations.