There were a few mysteries in opera 44.0.2510.857 so I completely removed it and reinstalled 44.0.2510.1159. Works much better all around. Youtube has an audio icon which mutes and unmutes; I thought it was a volume control so ignored it. Problem solved.
Settings > Browser > Languages. Choose it as a Preferred Language if you want to see websites in it, and add the Arabic dictionary if you want the spell checker. They don't seem to have Arabic as a UI language (for menus and such), sorry.
Your second screenshot was right-clicking on a word marked as incorrect, and the Spellcheck option was missing as expected. The first screenshot was not marked as incorrect (no wavy red underline). Again as expected.
If you want to request that Spellcheck show on both menus (a feature request), you can do that - but currently it is behaving as expected.
For some reason, I did not do what I always do when I make a software change and reboot. When I did, there was no problem with anything I wanted to do.
But, because this was my first (and last, now :rolleyes:) post, it was moderated and couldn't edit, reply or delete it until it went live which I was never notified about.
I will not bother coming here again with questions.
This means that you are using a very old version of Opera and, consequently, a very old version of Chromium since Opera stopped supporting Vista a while ago.
And the older the browser version, more are the chances that pages start showing issues.
Anyway, you can try deleting cookies and cache to see if it helps.