Replaced battery - now I have lines on the screen

you clearly damaged the screen or (worse) motherboard
when opening a google pixel, theres tiny components around the connector, and has a gold mark in one corner or side which is the ONLY safe place to pry up the cable from, otherwise you knock caps off
you likely missed that

Unfortunately it does look like the screen got damaged in the process of removing it. Looking at your picture it's unlikely the damage is on the motherboard; I have a high degree of confidence that replacing the screen will fix the problem. My guess is that in the process of separating the screen from the frame, some of the delicate connections between the flex cable and the glass that the display circuitry is printed on got disrupted, resulting in the issues you're seeing. That's not to say you did anything wrong whatsoever; a professional shop could have done the exact same thing.

iFixit has a guide taking you through the process, although if you've replaced the battery then you've already done all the work necessary to replace the screen.

Google Pixel 7 Pro Screen Replacement - iFixit Repair Guide

iFixit sells genuine Google replacement parts so if you buy the screen from them you'll get the best quality screen possible and a lifetime warranty. One thing to be aware of is that most vendors will allow you to return the screen if it doesn't fix the problem. So what you do is remove the original screen when you get the replacement, then just plug in the new one and test to make sure it works correctly. If it does, go ahead and finish the replacement, and if not you can return it for a refund as long as it hasn't actually been glued down and installed.

That being said, that screen is pretty expensive and it's completely understandable if you want to look for a cheaper alternative. Generally the cheapest ones are LCD based rather than OLED, but those use more battery power and their resolution isn't as good, so unless you really need to go as cheap as possible, I'd recommend staying away from them. The three main places I fall back on are Amazon, eBay and AliExpress. Amazon generally has the fastest delivery, but the prices are a bit higher, although there are some great deals at times. AliExpress has by far the lowest prices, but sometimes takes a while for shipping from China, so if you can wait that can be a good option. eBay is usually somewhere in the middle; shipping times are reasonable and prices are moderate.

As far as any hope of getting the current screen to work, about the only option would be to open the phone up again and check the connector. Unplug it and check both sides with a magnifying glass looking for any bent or broken pins. Bent pins can sometimes be straightened with some fine tip tweezers. Examine the flex cable as well for any dings or breaks in the traces. Assuming it all looks good, clean the connectors on the flex and the motherboard with 90% or higher concentration isopropyl (rubbing) alcohol (don't use the 70% stuff we all have lying around; it has impurities that can leave contamination on the board), then plug it back in and retest. That's really all you can do; if the problem is anywhere else then you'll have to replace the screen to fix it.