Are 2 a levels and a btec still good?

So,I intend to go to Durham sixth form but to study 3 a levels you must get 6s in everything which I definitely can’t do. I want to do classics,history and politics. But,if you get 5 5s you can get 2 a levels and a btec. Do you reckon I’d be able to potentially do my desired 3 alevels if I get a 9 in history and 8s in English plus high grades in dt and rs. I’ll likely only get 5s in everything else tho

If your taking about a BTEC Level 3 National Extended Certificate, then it is the equivalent of one A level and most universities will be happy to accept it as one (if uni was something you were considering). Do you know what subject you might take the BTEC in?
Also (and it may be too early for this), but do you know what you might like to do after sixth form? If you're thinking of university, is definitely worth checking the entry requirements of some degree subjects you might be interested in - just to make sure the BTEC isn't going to be an issue. (For most courses at most unis it won't be - but it could be for some.)
As you whether Durham Sixth Form would relax their normal "6s in everything" rule if you did particularly well in some GCSEs, I've no idea I'm afraid. Only they can probably answer that (or perhaps someone who's been in the same situation in a previous year.)

Hi sorry I’ve took so long to reply. I’m intending to take law at btec if I have to as it’s the only option I’d want to do. Later in life I want to pursue politics.

Are you anticipating attending university between your time at Durham Sixth Form and your pursuit of politics "later in life"?
The reason I ask is to ensure you check that your qualifications will allow you to access the degree course you want at the university you want.
As you're clearly based in or near Durham, I've checked the entry requirements for their BA Politics degree (details here). They say their entry requirements are "A level offer – AAA including a social science or humanities subject." On this page that say that if you're taking a BTEC Extended Certificate (which is what I assume your Law BTEC would be), they'd want "D + AA at A level".
They also point out that for "some courses you will need A levels in certain subjects in addition to these grades", by which they're referring to what's said on the BA Politics page that they want one of your A levels to be in "a social science or humanities subject".
So for this course at this university, one BTEC Extended Certificate and two A levels would be fine - as long as at least one of the A levels is a social science or humanities subject.

Hi,that’s calmed my nerves. I’ve been so worried i won’t be Able to get anywhere if I didn’t have 3 a levels . After sixth form I intend to go to Durham uni straight after. I’m guessing classics and history classes as humanities?

Correct, they'd both be classed as humanities.
(But don't put all your eggs in one Durham-shaped basket. It's quite competitive, and you have up to four other unis to apply to at the same time.)