It sounds like you have receives scam/phishing emails and they are common. If you clicked on any of the links in the emails, you need to run your antivirus and antimalware programs. If you don't have any antimalware programs, download and install Malwarebytes Antimalware (it's free) and run a full scan with no other programs running. Once you have run that and your updated antivirus program, change all your passwords. If you clicked on the link and logged in, they now have your username and password and will try to hijack your account.
Moving to Gumtree is pointless as it's owned by eBay and there are more scammers on there than there are on eBay. These emails did not come from eBay, they came from scammers. Never click on links in emails, especially from eBay or PayPal. Always go to the eBay or PayPal site and log in from there. If you are ever unsure if an email has come from eBay, check in your My Messages as emails that go to your inbox, also go there if they are legitimate. Another way to check is to hover your mouse over a link (DO NOT click on it) and it should show where you are being redirected to.
You can also right click on the email and select properties. When the box comes up, select view message source. If you look at the addresses in there, it will show whether they have come from eBay or someone else. Scammers are very good these days in making emails look genuine. EBay will also call you by your full name in the email (although that is no longer reliable as if you've had dealings with the scammer they will have your full name and be able to add it to the scam email).
Do not log into your online banking or anything else until you have done all of the above.
