Need help SM-N900S

first SM-N900S has only 2G network and i try to make it working on 3G but it become Unknown Baseband and Imei and than i flash SEC backup phone have basebank and imei (000000000000000) and also flash EFS backup too but phone limited service.

now i want to fix that so how can i fix it?:(:(:(:(:(

plz anybody advice me:):):):):)

thank b 4 hand