Hi ninanina123, let me ask you for a little more information:

New window - home page

When you launch a new window (using the menu or Command+n) you should see your home page, Google. If you don't, could you check the setting: How to set the home page.

New tab - thumbnails

When you launch a new tab (using the menu, the "+" button on the tab bar, or Command+t), you normally set Firefox's new tab page, which has a search box and thumbnail images of pages from your history. If you get a different page, most likely an add-on is customizing it.

Was that the new tab page you had before this problem started, or were you using an add-on to switch the page to Google?

Thanks jscher2000. Yes I use an add-on to switch the new tab to use my homepage, which I have set as Google. I've double checked Preferences and nothing has changed there

However I did just click on 'Home Page'/'Restore to Default' and then back to use Google again and for some reason my New Tab now works as it should and opens Google... very odd...

I just re-started the Mac and it has gone back to giving me the Donate Page for a new Tab.... strange

Think I've found the problem... Under 'Menu' I noticed an item called 'Tab Settings' and when I click on that I get a page I've never seen before as follows...

Under 'Option' it had something like about:blank so I changed that to Homepage and it seems to be fine now...

Can anyone tell me what this page 'Tab Settings' is all about and can I get rid of it?

This page has "kontakt@agenedia.com" on it

I've also just updated one of my Add-Ons.... This one:

New Tab Override (browser.newtab.url replacement) 6.0 .... I previously had v5.0

I've restarted again and all seems ok now

I'm glad you figured that out. Hopefully the new version will be stable and hold your setting!

If there is an ongoing issue, there is a simpler add-on you could use since you want your home page on the new tab:

https://addons.mozilla.org/firefox/addon/new-tab-homepage/