GSC
1) check which pages rank in top 100 (preferably in top 50) but not in top 10 and work on those to improve their rankings by building internal links to them (using exact match anchors, but not overdoing it) from relevant pages within the same silo / category... also by building external links to those pages, also with exact match anchors and also while not overdoing it

(partial match anchors could work too)
2) check the crawlability and indexability reports and fix accordingly. Technical SEO is a big part of ranking in google and if your site has crawlability / indexability errors this will prevent your site from ranking well... or ranking at all even (if the errors are numerous and big)... On the same topic (although not necessarily related to GSC) also make sure your website is mobile friendly and has good speed and CWV scores. I've heard someone say a while ago that google doesn't even care about indexing sites that are not mobile friendly, so this could be important...
3) check the relation between impressions, clicks, and CTR for each page (or at least for each page that's important to you) and figure out what can be done to improve that page's rankings (or at least traffic as sometimes more traffic is better than higher rankings).
For example...
a) if the CTR and clicks are low but the impressions are high this almost always means that people are seeing your page in Google but don't click on it for various reasons (usually the meta title and / or description are not compelling enough for them to click, so rewrite those to make them compelling enough - albeit still keep them relevant to the landing page - for people to click through on your site)
b) if the impressions are low but the clicks are high it COULD mean (but might not always be the case) that there are bots clicking on your page which - when left unaddressed - could actually affect your rankings. So fixing this issue (probably by putting your site behind Cloudflare or similar and implementing captchas) could help get rid of the bots which - in return - will help keep your page ranking
c) if the CTR is high (say over 20% for example, although some people might argue that this is not high CTR - and they could be right as it depends on a lot of things like niche, keywords, etc - but for the sake of this example let's assume that it's 20% or higher) but your page already ranks #1 in google for its main keyword and - at the same time - the impressions and clicks are both low this could mean that the keyword is not getting enough traffic, but it could also mean that google - in their scumbaggery - is sending all of the good traffic to other pages that rank lower than you (I've seen this happen) without letting you know.... well, they're not obligated to let you know anything that they do with their products, but still, it would be nice if they were nice
But business people are not nice, they only think and feel in terms of profits and ROI, so it's up to you to figure out why you rank #1 and have a good CTR for a keyword that's supposed to have decent traffic but you're getting none / very little of it.
In this case, check out what your competitors for that keyword are doing with their pages to get all of that traffic and mimic their success (you'll have to carefully analyze their page to figure out, of course, so be ready to work) and then beat them by improving on the successful elements of their page and - if all goes according to plan - google should divert that traffic from their pages to yours.
GA4 (although I'm not sure that these things still exist in GA4 as I've heard people say that GA4 has gone to shit, but you can try to see if they still exist)
1) have a look at the on-page elements that google considers important (time spent on page, bounce rate, etc) and try to improve those...
A decent amount of time spent on your page / site (especially if it involves a lot of engagement like clicking, scrolling, highlighting, etc) means that your visitors are interested in your content and this tells google that your page / site is important and this can improve your rankings
A low bounce rate has the same effect (it tells google that your page is important because bounce rate means that people don't leave your site for at least 5 seconds when they land on the entering page, which means that they find the content good, which further means that google can see this and reward you with better rankings)
Low bounce rate can mean anything under 20-25% I would say, but depending on circumstances (niche, type of content, etc) can mean under 50-60% in some cases... But anyway, aim for a bounce rate of less than 20% and you should be good, generally speaking
2) if you're selling stuff on your website you want to create and track goals (well, they were called goals in the old GA, I'm not sure what they're called now, but the principle should be the same) and track each step of the sales funnel (I'm assuming you already have sales funnels set up, otherwise you could be missing on a lot of money and intel)
So, you would check the GA4 goals to see where the potential customers get lost in the sales funnel process and - depending on the step they get lost at - you can fix / improve that step to retain the customers and further make them go to the next step into the funnel...
There are definitely more things you can do with GSC and GA4, but I can't think of them at the moment, but hopefully someone else chimes in too with some helpful answers. In the meantime, get busy with these and try to analyze and observe as many stats and things happening with your pages and I'm 50% certain you'll be able to come up with important observations yourself
