Greek letters are not stored correctly in mysql database

I have connected to a mysql database. I have setup the collation to utf8 and utf8_genetal_ci but all the time i try to save a greek word, the word is stored in database like ‘???’. I have the same issue in the past with php. However i overcomed this in php using this

query("SET NAMES utf8");

I have set the locale in appsheet to Greek but this is not solve the problem.

Do you know what is the problem?

Thanks in advance.

Is there anyone that has meet the above problem? I have seen that there is same trouble with spanish characters.
Is there any solution for this?