How to change languages?

Hello,

to begin with, i’ve watched the language setup video but i can’t get the language setup to work correctly. I am using the Loco translate Plugin as you recommended. I have added 3 languages, lets say English, Greek and Serbian for example. In wordpress under settings->general i have installed English and Greek and chosen English as Display Language.

Now when i go into my website, and choose Location from top left it seems to have no impact at all in the language. I also tried to enable Geo User Languages but this does not seem to work either.

What am i doing wrong?