Newcomer Needs Help :)

Jan 17, 2016
Hello community

well i'm french and i recently bought this phone.
Here are its details :

Device : HM 2LTE-SA
MIUI Version : MIUI 15.1.23.Beta
Android Version : 4.4.4 KTU84P
Core : 3.10.28-ga67e997

I'm getting pissed off by these constant app adds pop-up.
So I've installed the app Adaway with a custom host file to get rid of the adds but it doesn't help it.

Please you guys tell me how can i fix it! :/
for info i have no experience about how flashing a smartphone.

thank you!