Choosing highers

Okay thanks this has given me so much guidance.i will probably do NAT 5 this year and higher next year

From what I've seen, human bio and Modern Studies are some of the hardest subjects to do well in so unless your really interested, stick with politics (and normal higher biology if you want, which js easier).
If you want to go to university or college, check the requirements. Higher English and some form of n5 maths (sometimes they allow n5 apps instead) are normally required, so there would be a high chance of you needing them.