HELP !!!! Engine problems

[1badassaudi]

I have a 2004 Audi Allroad with only 20,000k that got some front end damage from an accident about 3 years ago. I couldn’t find any parts used and the dealerships prices were crazy high so I decided to park it until I found the parts to fix it. Well now it’s 3 years later and the car has only 20,000k and I found all the parts. So first I sent it to a local shop with the front end disassembled and had the do the timing belt, tensioner, pulley and one of the timing belt cam gears I think its called because it had a nick in it from the accident. The timing belt never got damaged or came off but I wanted to change it while I was already in there. After the shop put the belt on and sealed it with al the covers I took it away to my garage and put the whole front end together rad support, rad, intercoolers fans, lights etc . Once I got it all together I filled all the fluids and double checked the levels. Finally ready to start the car when I started it the car made a really loud diesel knocking sound so I shut it down. Checked everything again and it looked fine. So I started it again and the same thing. Now after the 2 starts it will not start anymore it turns over but will not start. Is this bent valves? Did they install the timing belt wrong? How can I tell if the valves are bent? Please help me what should I do?