Create Webpage for Sellers and buyers of ad spaces

I bought a "homey" wordpress theme and need someone to install, adapt and change it for me on Wordpress. The website is about booking advertising space. Customers can upload advertising spaces here and those interested can book or inquire about them. Therefore, both advertisers and bookers must register for the service and have an account area. Correspondingly, mailings with attachments must be set up for inquiries, which must be forwarded by the administrator after check. The theme offers everything, but you have to change it in the right places. Therefore, I need someone who can not only make administrative changes but also do simple coding activities. I have certain ideas for the pages - but you are welcome to make suggestions on how you would implement the pages pragmatically. It is better to kerp it simple. Please let me know if you can implement this. One more thing: I had already installed it and tried something, so you would have to uninstall it first. If you can also set up Mailchimp and WPML. It would be great because it should be used for Germany. At the End i need also a new design. Important for me is, 1. People can offer their adspaces (different ad space categories) and as an admin i will be able to release that on the webpage. 2. agencies or companies can make a request for the the offered ad spaces - and as an admin i will be able to forward that to the adspace owner to get their ok. Afterwards the admin will send a notice to agency that they could contact the ad space owner. The Messages should be managed by system and shhoudl also have standard pdf documents. Maybe you have an idea to handle that kind of business. Important plugins for me are 1. WPML - i think it is the Language plugin | 2. SEO Plugin | Speed Up Plugin (cash) 3. Tracking & Reporting Plugin | 4. MailChimp with alligned Mailtemplates | any other from your opinion? The page must be ready to use and responsive. Now it's your turn. what is you suggestion? regards