I was wondering if there is a chance to sell a service based company (providing marketing services) and who will buy it?
YES! You certainly can sell a services business; and, if it is positioned and prepared properly, for pretty great returns too. There are a number of different exit strategies available to you, not ALL of them acquisition. For instance; we have helped service business owners transition (exit) from their business without selling the business, but instead by retaining a minority interest and receiving large (7 figure) royalty checks for years after their departure.
That said, IF acquisition is what you want each of the dozens of strategies available to you really begin with identifying prospective buyers, understanding their motivation for acquisition and pivoting your company into alignment with those motivations.
I explain the process in more detail here: http://www.zerolimitsventures.com/cadredc
Hope this helps! Good luck.
Steve