Firmware of your W9980 is up to date? What's the version of it?
Provide screenshots of status page when it is working and stops working.
How often does it happen? Does it reconnect normally?

I have attached a screenshot of the status page.

It stays the same when it disconnects.

It does reconnect normally?         

It can happen every couple of minutes or every hour. Depends.
Firmware version: 0.6.0 1.12 v0021.0 Build 150507 Rel.40130n
Hardware version: TD-W9980 v1 00000000
Please help. It is really unbearable

When it disconnects, neither wired connection nor wireless connection will work, right?
Can you ping google.com or ping 8.8.8.8 when it disconnects on your PC?
Try to Set DNS server manually with primary DNS 8.8.8.8 and secondary 8.8.4.4.

I tried it. I put Google DNS servers but I still get the disconnections. It thappens both on the wireless and the wired connection.

yakovyarmo wrote

I tried it. I put Google DNS servers but I still get the disconnections. It thappens both on the wireless and the wired connection.

Did you check whether the router reboots during disconnection? I had a similar issue, for me the router rebooted quite often and reconnected on my w8968 v3. Disabling igmp snooping did the trick. I would suggest the same.

http://forum.tp-link.com/showthread.php?81892-TP-LINK-TD-W8968-V3-reboots-randomly-and-limited-Windows-10-support

Will try. What is the meaning of disabling that? Is it important?

The wifi still hangs. Any suggestions?

When it disconnects, go to Diagnostic and check if there is any error in test result. Provide a screenshot pls.
Is it a brand new router? You may try to get a replacement to see it will be solved.

What do you mean by a replacement ?
And I cant go to diagnostic because I can't reach to the modem

It didn't help. What else can I do?