406 Not Acceptable and server not responding in website and admin

WordPress beginner here.
So I have been working on my website for a month (https://www.papertradelinks.com) and the past couple of weeks I haven’t had any problems since last week when my website started showing the 406 Not Acceptable Error. This error, and the server not responding error (either one of them came, Its really occasional) always showed up everytime I tried to login to wp-admin or my own website. Not only that, all my devices on my home network face the same problem. The problem is temporarily resolved after restarting my router after 10 minutes and clearing cache, and I can login to wp-admin again, but even the slightest modifications I try to make to my website make the server unresponsive again and the website and wp-admin stop loading again, and I have to restart the router again to make it work.
So I thought it was a problem with my URL or network, but after trying to edit my website (wp-admin) from a different IP (my friends computer) I faced the same problem of 406 and server not responding. Restarting my friends router also made it work temporarily, and it was the same story all over again, that too from a different IP!
I also tried to access my wp-admin and website from proxies, and they were able to access, but again after I tried to edit anything in my wp-admin through those proxies, even the proxies showed server stopped responding and 406 Not acceptable!

By now, even my cpanel shows server stopped responding.

So I looked up about it online and found about the .htaccess file. I tried to find this file in my directory and couldn’t find anything like it (I checked the show hidden files), so I created a htaccess file and pasted this into it:

<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>

I couldn’t name it .htaccess and upload it while its hidden so I renamed it in the File Manager in cpanel to .htaccess.

Still nothing seems to work. Please help!