TRYING TO CHANGE eBAY PASSWORD

I had an experience where someone stole an ebay package from a FedEX delivery and somehow seemed able to hack into my account and change things. That is all I can figure.
I am now trying to change my password. This thief wrote an email to eBay thanking them for the rapid service-stole my account, package, and identity. I am now trying to change my password to a new one. May change the username also.
I am new to all this and it is not easy. Also I cannot work the 3 dots and ettings incrome it goes to Sync and says it is turned OFF. I do not know how to work with all this. Wondering if using quick restore would be of help? Been with computers since the 1980's and 1990's and never had an issue. Now seem to be having MANY. Scary.
How do I turn Syncing back on so maybe I can access Google Chrome Settings. It says Syncing and says "Turn Off" so something is not working right.
Also how do I change it so a HUGE window opens on my desktop instead of a smaller one I can adjust, move or do anything but CLOSE? Suddenly HUGE screen sized windows are opening and all I can do is close them.

 

20 or 30 years of buying online with no problems and then all these problems. Cannot remember full sized windows oping on dektop and borders are hidden off screen and if not they do not adjust anyway but just stay oversized. All I can do is close them. The minimize and maximize options are hidden by the screen borders.

 

I think I will also read the eBay account protection suggestions.