there was a google update recently (finished like 4-5 days ago), so you've been probably affected by that update, in which case - unless you know for sure what to fix - I'd say that you wait for google to fix it first, because I've heard that they've messed the SERPs quite a lot with this update. So, probably it's their fault, not yours, in which case waiting a bit longer might save you from ruining your site completely
So, give it 2 more weeks or so, and if the traffic doesn't come back it's time to start looking for fixes.
Since you've not given us any useful info that we can cling onto, I would say look into any / all of these things:
- content quality, relevancy and optimization, and intent matching
- anchor texts (brandable anchors are to be preferred these days over other types of anchors since google are trying to force everyone into branding themselves, so branding is becoming more and more important each day)
- internal linking (still a big thing in modern-day SEO, so try to improve it if it's lacking)
- topical authority and site siloing (ie. cover the main topic of your site in the greatest details possible, and also structure it in such a way that the stupid googlebot can find all of the relevant information in maximum 3 hops from the main hub which is the homepage usually)
- site trust and authority (if your site never had strong backlinks and / or high authority but you're competing with sites that do have these metrics you need to raise those metrics too, or you'll be left behind)
- with the infestation of everything by the AI it's also possible that the AI is serving the people the answer outright, which means that people have no reasons anymore to visit your site, which justifies the drop in traffic. Either this, or you've been completely outranked or de-ranked by google or by your competitors.
So yeah, most likely it's one of these that did you dirty if you asked me, but I would still recommend that you wait (at least for 1 more weak) before making any changes, maybe things will get fixed by google.
In the meantime, analyze the sites and the pages that have taken over the SERPs, maybe you can find something that you can fix / improve on your site to match those guys' content / backlinks / whatever...