Learn Hardcore Greek: Μπορείς να φας ό,τι θέλεις στη γιορτή, δεν είναι πολύ αλμυρό. - You can eat whatever you want at the celebration; it is not very salty.

Μπορείς = you can / you are able (2nd person singular of μπορώ)
να φας = to eat (literally: that you eat; φας is the aorist subjunctive of τρώω, “I eat”)
ό,τι = whatever / anything that
θέλεις = you want (2nd person singular of θέλω)
στη = at / in the (contraction of σε
- τη)
γιορτή = celebration / name day / party
δεν είναι = it is not
πολύ = very / not very
αλμυρό = salty (neuter singular form of the adjective αλμυρός)

So structurally:

Μπορείς να φας
→ You can eat

ό,τι θέλεις
→ whatever you want

στη γιορτή, δεν είναι πολύ αλμυρό.
→ at the party, it’s not very salty.

Why is it να φας and not να τρως?

Both are from τρώω (to eat), but they express different aspect:

να φας = aorist subjunctive → focuses on the completed action (“to eat (once / as an event)”)
να τρως = present subjunctive → focuses on ongoing / repeated action (“to be eating / to keep eating”)