Wireless Connection Unstable

My router is D-link and Linksys (I don’t know if its working as 1 or 2). I do not know much about routers.

These few days, the connection was unstable and we were not able to play any game without disconnecting quite often. We checked the security login to connect and it was activated. Can anyone suggest some ways so we could try and solve this annoying problem?

Off-topic : I do not know why my email and password was wrong when I got back to this forum and I created a new account relating to the first post I made.