My router keeps saying offline R6120

[Sway-4-tay]

My router will work for a bit but it’ll trip up and stop working and I use the completely useless app night hawk “internet: offline”
It says I’ve restarted it does the same thing I restored it also to factory settings worked like a charm for a bit then it just went offline again.. frustrating product

[plemans]

what modem/gateway is it connected to? 

What firmware is on the router?

When it drops, do devices still connect but say "connected, no internet"? or what error issue is going on in detail?