Tips for GCSE math?

I'm in year 11 right now, and we're doing our mock exams soon (can't be certain). I'm in the second highest math group because in year 9, I found it all really easy and just spent every lesson on Facebook and got all A's and A*'s without revising.
But then in year 10 I got put in set 2, and set 1 and set 2 classes do IGCSE extended maths as well as Additional Maths.

Unfortunately, I discovered that I was only good at algebra and so started actually studying for tests, but I always get B's and C's, even if I try really hard. Unless it's algebra related, in which case I usually get over 90%.

The lowest grade I've ever gotten is a D when I got 49% in trigonometry. I actually tried really hard.

I'm also really good at mental arithmetic and the non calc papers. It's usually on the calc papers where I screw up.

I don't really know if there's something wrong with my brain which makes it switch off whenever algebra isn't involved.

Anyone else in my situation? What did you do about it? My main areas of concern are trigonometry, geometry, probability, inverse variations and sets.

They expect everyone in our class to do Higher Level Maths in IB, so I'm really worried

Thanks!

I have problems with remembering the formulae, applying sin, cosine and tangent, and bearings for trig