safari cannot connect to server

I do have intego antivirus, but i’ve disabled it.

Merely disabling non-Apple "anti-virus" junk is an insufficient remedy. It must be completely, irrevocably, and permanently uninstalled in strict accordance with its instructions.

Rule 1 of Macs is don't install junk.

Did you restart your Mac?

Here are some additional troubleshooting steps to follow, in no particular order:

• If Safari doesn't load a page or webpage items are missing - Apple Support
• If Safari is slow, stops responding, quits unexpectedly, or has other issues - Apple Support
• How to use Internet plug-ins in Safari for Mac - Apple Support
• "Safe Mode": Use safe mode to isolate issues with your Mac - Apple Support

  Determine if the problems exist in Safe Mode. Then, restart normally.

If you don't get anywhere, you can use the following procedure to determine if the problem is internal or external to your Mac. Causes may involve your router, your ISP, the DNS Server(s) it uses, or certain user-configurable options.

1. Shut down your Mac.
2. Load macOS Recovery by holding ⌘ and r (two fingers) while you start your Mac with a third finger.
3. At the macOS Utilities screen, release those two fingers.
4. Choose Get Help Online.
5. Safari will launch, but it will lack your bookmarks, favorites, history and other preferences.

Determine if the problem persists while using Safari in that mode. After that, restart your Mac normally, and reply with your observations.

Back up your Mac prior to making any changes to its file system. To learn how to use Time Machine please read How to use Time Machine to back up or restore your Mac - Apple Support.

You effectively isolated the problem to your Mac. Something broke its ability to connect beyond your local network, a possible consequence of installing "Intego" or something equally odious. Any number of non-Apple "cleaning" and / or "security" products can also be responsible. Those things are very popular and highly successful scams. If you installed anything like that, the only practicable solution is to erase the Mac and reconfigure it from the ground up.

Another thought is to confirm your Mac's system time and date are correct for your geographical location. Secure websites won't load unless they're correct.

If you think it's related to Dropbox it should be simple enough to uninstall it, and determine if the problem continues. As I understand Dropbox your files will still remain available on their servers, and you can always reinstall Dropbox again.

The only remaining suggestion I have is to reinstall macOS: How to reinstall macOS - Apple Support. If that proves unsucessful, then Contact Support. You may have to pay them to help you undo the damage.

scavenged all safari stuff in both the user and system libraries

With the understanding it's not possible for me to know exactly what you did, reinstalling macOS should fix whatever damage might have occurred as a result.

My Time machine is backing up to my Synology server quite happily too.

Those backups are not and will never be reliable. It's another story altogether. To learn how to use Time Machine please read How to use Time Machine to back up or restore your Mac - Apple Support. Non-Apple NAS devices are not supported and will never be reliable.

Please read If Safari doesn't load a page or webpage items are missing - Apple Support.

Needless to say, if you are using any non-Apple "anti-virus", "cleaning", or "Internet security" products, anything at all in that broad category of utterly useless garbage, don't. A lot of things won't work if you do.