Technical cleanup and clearer service pages can be done in weeks. A change in how often the right people find you takes longer, and it depends on competition and on whether the pages deserve to rank.
Do not promise a position. Do promise the work: pages that match real queries, a site that can be crawled, and a way to see enquiries rather than only visits.
If leadership needs a result this month, paid or a clearer sales path is the honest tool. SEO is the asset you build beside that.