Software for the advertising market sought

I am looking for software for the classifieds market, as a content management system (CMS). An IT service would also be an option.

The software (IT service) should meet the following requirements:

• Posting ads in the following areas
• Events
• Real estate
• Vehicles
• Newsletter
• Messages (communication between sellers or providers and potential buyers)
• Sitemap generator in XML format
• Web-based
• Can be viewed on smartphones, responsive design
• GDPR compliant
• Purchase solution preferred
• Cost-effective

For the future, with the possibility of expanding the advertising market as a business, then with plug-ins such as invoicing, accounting, etc.

One software workstation is planned. A Linux web server will be used.