Me and my friend are on the same server (both lv 7) but cannot find each other on the game. Any reason..

Maybe you are in different lines. Every map has 'line'. Just click in the corner where you see the server time, it will open the map. It is a button that say 'Line ##' with the number, it can be Line 0, Line 1, Line 2... The quantity depends on the map, some have only 0 or even 12, just pick the same line in the same map and you will be able to see each other.

Also, you can team up. Just add each other, click on the avatar where you chat with ur friend and click 'Invite to join/Request to join', then follow and you gonna appear where the leader is.

Hope any of this will help.