I’m trying to create a web shop that I would be able to add multiple sellers to, but I have no clue where to start because every time I search something I’m just flooded with all kinds of information about irrelevant crap like Shopify, and Etsy, which doesn’t help.
Are you trying to host everything yourself? Right now, your best bet is WordPress plus pluggins, but I would honestly recommend using a vendor to do this so that you don’t have to do all of the PCI Compliance stuff. I have done this for stores in the past and the regulation is very stringent and the solution is very fragile.
I have worked with these two in the past, but like @lathama mentioned, there are many out there. I would do a YouTube search to get some options of what is out there and how the maintainers felt about the integration into their CMSes.