Finally rooted, my hint to all is,
Initial foothold,
find out what u can read and try to read some files that are related to the app, then try to figure out what is removed.
PE,
This is something that i have not done before but basically to check “capabilities”. Read up more at https://packetstorm.foofus.com/papers/attack/exploiting_capabilities_the_dark_side.pdf
Hope not too much of a spoiler as this is something not so common.
Really enjoyed this box and also thanks @nomad17 for the hint. 