Yup, PWA is progressive web apps - so you'll have your classifieds site posted as an app in Apple / Google app stores... helps with extending site reach as any sound site strategy should include mobile and have mobile as the primary focus.
As for Cloudflare, and seeing that you're targeting the world, I would highly recommend it for several reasons:
1. Cybersecurity - through WAF and other must-have site security features ie. Bot-fighting, Invisble Captcha(no-script), hot-linking etc.
2. CDN - I noticed your site is hosted out of the Netherlands which is great as that country hosts one of the top 5 internet exchanges in the world but it mainly benefits mainland Europe. By implementing and fine-tuning Cloudflare / caching (you can start with the free plan), you'll ensure your site is fast and performant globally. Also, Google and other search engines love fast sites (mobile / web versions).
3. Cloudflare is synonymous with privacy - highly recommended for GDPR jurisdictions. They also offer privacy-focused site analytics which I think you get the basic version with the free plan. You can also opt for Matomo (open source, easy to install and it's free).
4. Speed .. You get http3/QUIC out of the box which accelerates site access. Also, Cloudflare has the most POPs (Points of Presence) in the world - so a customer of yours in the US would get served by local/regional pops (static / cacheable content). Dynamic content will always be served out of AMS/Netherlands but it will get served over Cloudflare's networks which are optimized for delivery / shortest path.
While you may have secured your site using a firewall, it isn't sufficient to defend against today's attacks and cybersecurity challenges. Cloudflare adds that missing layer of protection and speeds things up for your site audience.
As for the pages - yes, I meant the static pages. I noticed you had them hosted under / with your categories also hosted under / ... usually with Osclass, you can have one or the other but not both which honestly makes no sense as wordpress is capable of doing that out of the box. Did you modify your core files?