Are my sentences grammatically correct?

[hardworker]

I have been learning English for ten years, but my English is still not very good. I need to work hard to improve my English skills. I would like to make up two sentences below.

(ex) Soccer commentators are having a TV discussion about how five popular Team A players will perform next season. They believe that three will improve their goal tallies while the other two will regress to an unsatisfactory performance.

Are there any grammar mistakes? Are there any words that I have used incorrectly? Please help me. Thank you very much.

[Alan]

No problem in terms of grammar, but the expression 'regress to an unsatisfactory performance' is not idiomatic or even very clear in meaning.

I suggest you try to rephrase.