every time i open a new tab, a new window homepage shows up

Ah- I gotcha. Unfortunately, it seems you have adware on your computer. (I like John Galt's tongue-in-cheek User Tip about this - How to install adware - Apple Community)

Search Marquis is a common one- it hijacks your browser to generate clicks and ad revenue. Luckily, it's not dangerous, and can be removed easily enough. The easiest way to fix it is to get the free version of Malwarebytes. It's a safe tool that helps remove malware from your computer, and the free version should suffice. You can get it here. Quit Safari, scan for malware, then quit it when complete. Hold Shift and open Safari, and you should be good.

If the problem persists, it may need to be done manually.

To be clear- when you open a new tab, it opens a different page than New Tab?

I am currently having the same issue. Can you update later on if it was successful?

Glad to hear it!