I'm doing my grade 6 in march.

I'm doing
Sonata in F
Prelude in C# minor
Rumba Toccata

Can anyone give me any tips for these pieces please? And how do you get a good mark in scales???

For a good mark in scales you need to respond promptly (but not so quickly that you don't get your brain in gear) and play with an even tempo and tone. Make them sound as though they are going somewhere.