Finally succeeded doing this. As stated by others it is important to get to know the mechanics of this meta and be in a group that generally understand these mechanics as well. Main problem is that maps are constantly full so finding a decent group is not so easy. The group I was in was also in a filled map. Somehow after trying dozens of times I got in but at that point all preps were already maxed out so i could not get my maxed stacks within time anymore. So I could not open all reward chests at the end....sigh.
A few things though, I am not so lucky with the extremely crowded environment, especially the last phase. Normal oversight over the overall situation is difficult due to loads of players, foes, bubbles, water spouts etcetera etcetera. I also do not fully understand the tail which sometimes you have to break bar and sometimes not. When does this happen? Also the apparent rage mode at the end. So still a lot to learn.