Lenovo S650 internet problem?

I'm wondering why is the Wi-Fi connection from my Lenovo keeps getting disconnected even though the internet is fast?

What seems to be the problem with my new lenovo s820?

I just bought a lenovo s820 last 2 months now the phone has gotten slow I though it has caught a virus so I had to factory reset it

but it is getting slow again and especially when I'm playing angry birds go it suddenly closes. Also tetris and another thing that happened is when I open the browser and also google chrome it also suddenly closes. This time instead of factory reseting it again I just powered off, removed the battery, put it back then powered it on again. It is working fine but I'm still worrying what if it happens again?

I mean what seems to be the problem of this phone why does it suddenly becomes slow and suddenly closes apps? I scanned it before with the built in norton mobile but it says no virus has been detected. I also haven't installed apps outside of what I download from the google play.

Adreno 305 vs powervr sgx544?

Which one is best while playing high end games. Because moto g is having adreno 305 and lenovo s920 is having sgx544. And also which phone is best in all aspects among these two (considering specs, everything and neglecting brand ).

How to insert a new line when typing via Lenovo S820 keyboard?

I have Android 4.2.1 and I can't seem to find the new line button. Any idea?

Added (1). Here's a picture of the keyboard when I'm replying to a text:
That's the delete button above the smiley button

Added (2). Also that's how the keyboard looks like for all the other functions