Do you want to work on Loop Quantum Gravity? I have searched universities in Germany and only found FAU has professors working on it. But they have not had open PhD position pronouncement at least since 2013, when I found them. Also, when I wrote e-mails to them, they never replied me. So do you also find this institute? Or you find other universities in Germany having research groups in Loop Quantum Gravity?
You are similar to me in several aspects, so I am tempted to answer you. First, you are my compatriot. Second, I also did MSc in gravitation without taking the course Quantum Field Theory. However, unlike you, I worked on purely theoretical formulations of classical gravity rather than the applied sector of gravitation. Third, when I browsed papers of quantum gravity, I also had difficulty grasping the basic ideas therein because I didn't study Quantum Field Theory systematically. Nevertheless, I never think I need to take any course in order to understand them. I think recommending me books regarding Quantum Field Theory or Loop Quantum Gravity for me to self-study to lay the required foundations is enough. When I conducted my MSc research work, I also didn't take the course General Relativity. Actually I was not given the chance to take the course General Relativity because when I registered as a master student in my university, my physics department didn't have the course in graduate level—at that time there was the course General Relativity in undergraduate level taught by my advisor, but if I took that course, it wouldn't be taken into credit due to its being in undergraduate level. So I self-studied the prerequisite knowledge for my classical gravity research. Likewise, I didn't have the chance to take the course Quantum Field Theory because my physics department didn't have the course when I registered therein.