If you're a regular blogger, these are probably the topics you blog about most frequently. Or perhaps they're the topics that come up the most in sales conversations. Put yourself in the shoes of your buyer personas -- what types of topics would your target audience search that you'd want your business to get found for? If you were a company like HubSpot, for example -- selling marketing software (which happens to have some awesome SEO tools ... but I digress ... you might have general topic buckets like:
While Google is on record as stating these quality raters do not directly influence where you rank (without more senior analysts making a call on the quality of your website, I presume?) – there are some things in this document, mostly of a user experience nature (UX) that all search engine optimisers and Webmasters of any kind should note going forward.
Ask for a technical and search audit for your site to learn what they think needs to be done, why, and what the expected outcome should be. You'll probably have to pay for this. You will probably have to give them read-only access to your site on Search Console. (At this stage, don't grant them write access.) Your prospective SEO should be able to give you realistic estimates of improvement, and an estimate of the work involved. If they guarantee you that their changes will give you first place in search results, find someone else.