Literature base of a practical thesis. I need your help, Reddit!

Hello Reddit,

I have never needed help before, but since I am kind of struggling with my thesis and I think it won't hurt to try, I will state my problem here. Apart from working on daily business in a marketing company that works exclusively for Media Markt including print ads specifically for each store (and teams per country), I am working on a thesis to research the current workflow. In particular, I will be interviewing the markets about the problems they have, list them and list solutions / recommendations where possible. I've always been a practical kind of guy and I hate theory. But from school out I have been warned to have a proper theoretical foundation. This is where I am struggling: I can easily conduct a set of interview according to proper sampling and attention points for in-depth interviews. Apart from that, I have some theory about strategical decision making. But this is about as far as I am getting when it comes to theoretical foundation I can use for this thesis. Most information is specific for this market and comes from practical information rather than theories or literature. Maybe someone who has experience with this can give me a heads up since I am certainly worrying about this part. Maybe it's because I just don't like theory, but in the end I have to support it with theory or it will get rejected. Thanks in advance to everyone who takes the time to read / reply! :)