Some apps dont work with my mobile network.

I've got this phone a month ago,and it was allright, now, i cant use my mobile network to browse (not with chrome, opera nor with miui browser) facebook doesnt load from the mobile network, messager does lot but really not always, the only app working great with mobile data ia Clash of Clans.
Xiaomi Hongmi (WCDMA) multilang stable 5.0
Any ideas about how i fix it?
It wosnt working either with preinstalled rom , when i bought it , either with stable 5.0