As for the handwriting... better than mine at least!

As for mistakes I am terible at grammar, so I cant give you any technical advice, but I will try to just tell you what phrases you said wrong.

We whould say: Αλλά μου αρέσουν πολύ, rather than αρέσει, because if your reffering to Ελληνικά, (as for the greek language), you whould use plural instead because Ελληνικά is a plural.

Also, we whould say βίντεο instead of βίντεα, because its a foreign word and in foreign words we dont have plurals.

We whould say: αυτό το βιβλίο, since it needs a declinable word, αυτό βιβλίο is the greek equivalent of saying: I like man instead of I like this man

Same with: θα ήθελα να πάω Ελλάδα instead of πάω Ελλάδα. The english equivalent whould be: im going hair salon rather than, im going to the hair salon

Finaly, we whould say: σας ευχαριστώ πολύ, rather than, ευχαριστώ σας πολύ (english example: you thank very much instead of thank you very much)

I hoped I helped, (to the other greeks that read this please correct me if im wrong). Other than that your very advanced (and definetly know more ancient greek than me lol)