Difficulties beeing german in america and working for a big company?

So I started working for the Pantry as an istant manager (kangaroo) and got transfered 3 times allready, due to training and a manager switch. Im working in the same store as our district manager BUT the store I am in right now with my store manager is beeing permanently closed next day. Everybody seems to know but me, I found out yesterday from a coworker. So I left the district manager a note to please call me because I would like to know if im in need to look for a new job next year. He called me (really bad reception) and told me I might have my own store (store manager) by than. And I was like, ok so I wont be unemplyed? and he was like: if you suck and be a pain in the *** than you will be unemployed. I was kind of shocked that he used those words but whatever, he is way higher than me. I had some troubles with my first store manager since Im german and the language barrier got me sometimes, and she tried everything to get me fired. Now I have a really nice store manager working with me and we get along fine. But sometimes it seems that beeing german makes me an outsider in the store, sometimes they make fun of me for pronouncing words a funny way. And every now and than I take instructions the wrong way, because of missunderstandings. I try everything to be a good istant manager but what my district manager told me today kinda put me down. I have no idea how he meant it, Im worried he said that because I left him a note asking him to call me. Any advice or maybe somebody having the same problems???