That was a big SEO journey. We've started the wesite optimization and realized that the CRM (we can avoid names here, right?) is so sophisticated that we can do nearly nothing to technically optimize that. Ok, we've started with the keyword research and content creation, recognized a few long tails and local queries, placed some rewritten content for 100+ out of 21k webpages. We've been focusing on two things - how to highlight the client's services in Google search instead of just the business name ranking, and which pages to land vistors on in order to convert effectively. And success is coming - we've started to grow in organic traffic after 2 months of digging out.
The next big thing was the optimization - we do need it to get good results. Started to go deeper, we've revised some tricks of the CRM which helped to add some tags, optimize images and JS/CSS files, and so on. So, long story short, we've got 90 points out of 100 in Ahrefs thanks to our mad and nerdy developer, instead of initial 25. That was a big win! Also we've created the algorithm of new placements and optimization, to avoid issues in a future.
So, when 6 months are gone, we've got twice more organic traffic, but the main point is that it's a service-related one, so we've taken this traffic from competitors. And even more, we're keeping the conversion rate at the same level (well, almost), getting 80% more conversions than a half a year before. And, we're working with this client now, and continue growing.