Maths GCSE retake

Is it possible to retake maths after gcses, because im doing foundation(and im getting fives rn) and after results day I want retake my maths gcse to do higher and at least get a 6-7 and at shift to a better sixth form after recieving maths grade.

(science:6-6 - 7-6)
(English: 4s and 5s)

Yes, you can retake your GCSE in maths at any adult college for free (assuming you don't meet the grade requirements). You usually can take it at a 6th form, but this will depend on the individual 6th form.

If that's not possible, consider applying for your exams as a private candidate (you can take an online course in the GCSE at a cost, or revise the material through the books you use). To book your exams as a private candidate:

The exam and admin fees are set by the exam board, and therefore doesn't vary with the exam centre.

I don't know whether you can apply for 6th form after your GCSE and whether it's worth redoing your GCSE solely to get into a better 6th form. It's best to check with the 6th form colleges that you want to apply to first regarding your arrangements.
Do note, there is often an age restriction (e.g. 16-19) to when you can apply and do courses at 6th form colleges. If you leave it too late, you might not even get to do your A Levels.

what if i want to resit online?

thats impossible practically since covid restrictions are lifted everywhere

i meant like doing the course work online and resitting the exam at a place