How can I stop users from registering?

I am unsure if I have my settings correct; or if my page was hacked?

The other day I logged on to find a person registered as a user on my blog. Thankfully I recieved a notice in email through wordpress. I did a search on this person and found that he has signed on to several sites within “user”s and changes the content. One page I ran accross stated “Hacked by Swan” for a few seconds and then about two minutes later went to that sites correct homepage. His isp is not in this country and I believe it is in hebrew (?) gawab.com so I don’t think I will be able to get assistance there.

I deleted him and changed my Membership settings from “Anyone can register” to “Users must be registered and logged in to comment”. However now visitors are unable to comment. How can I place my settings not to allow others to sign on to my blog and make changes; yet, to make comments?

Also: I can not recall if he created pages or changed pages but I *think* I recall it saying 4 pages after his name. I have done searches throughout my blog concerning his name, his isp, words such as “hack”. Since I already deleted him is there a way to check this — or find his changed pages?

My site: https://ascenderrisesabove.com/wordpress/

Thank you all for whatever information you might have on this situation.