Safari can't find the server

Hi, lately when I try to open a window in Safari it say's Safari can't find the server, on pages I have opened before?? It happens allot and it's frustrating. I have plenty of ram on my McBook Pro. I'm still using Mavrick 9.5. and Safari 9.1.3. The server is one issue.

I'm not a know it all when it comes to computers and also need a little help on knowing which kind of files and caches and cookies and apps and I'm sure there are more things I can do in order to clear my mac for more space, in detail???!!

The other question I have I noticed in Network in the location section where the up and down arrows are I have 5 different location dates with time is that normal???? Can I delete the 4 that do not have a check mark? Or do I put a check mark on the latest date and delete the rest? Why are there 5 difference location with dates and time????

I hope what I wrote made since to someone because it is all very confusing to me😕......

How can I make sure that my Mac is save from hackers?????

Last is Google Chrome not doing updates anymore, is it dangerous for me to continue to use it without it doing updates????

Any help I can get would be very much appreciated!!!

Thanks feather6868