Issues with claud butler 2.7 alpina 2015 model

[steven bridges]

can any one help
I recently bought a claud butler alpina 2.7 2015 through cycle to work scheme, I had problems with brakes and gear slipping , the brakes I upgraded at a cost as they were not stopping me very well . upgrade from clarks exo skeletal to shimano deore , but I was charged a little fee, but im still having gears slip all time- when I take it back they tighten cable and it happens again. they said my deraileaur arm was bent straighted it up but still doing it- Im not doing any extreme riding just mainly flat trails for fitness so im not throwing bike around and I am carefull when I put bike away , any one got any thoughts

 

[steven bridges]

they have now changed the chain and the cable casing to the derailleur but im still having problems , they now saying as im abig lad I could be putting too much power through the pedals and wearing thisngs out, but they sold me the bike maybe they should have recommended a better one its really doing my head in, im new to cycling and this is killing my enjoyment - if I was told from start this bike may not be suitable I could have got a better one think they just sold me a old bike to get rid of it