What kind of damage can a timing belt do to a Fiat Scudo engine if the garage fitted it wrong?

depends how wrong ? as in how many notches out ,if worst case it will bend the pistons and damage valves to the point of engine is perminantly damaged loss of power then eventual non function ,i have the same problem in my car had belt fitted incorrectly or belt jumped or slip but engine now no good !! now saving for replacement engine !!!