Volvo s80 i had a fanbelt to break and replaced it and the enginee won't crank one guy said that that the engine kick back and bent a valve causing the engine to loose compression can you help me?

no
expect bent valves if the timing belt breaks

Timing marks must be exact. Did you check to see if valves were bent when the belt broke?

autodata publication 2012 states that it is an interference engine in which there is a possibility of valve to piston damage in the event of timing belt failure. It is mostly to occur.
if you are removing the belt as a precaution then make sure all the timing marks line up prior to belt removal and once the belt has been removed do not move anything
If the belt has broken you may check for bent valves by placing the head upside down and putting fluid into the combustion chambers around the valves . If it runs out then the valve is damaged
If you find one then check the lot
Basically it is professional mechanics to assume that the valves are bent anyway and have them checked before reassembly of the head.

Probably Caused by old engine and burnt deposits on the valves and spark plugs. Change the plugs, add cleaner to the gas (get it from Pep Boys)

You have no valve clearance, it definetly hit a exhaust valve , you will need a valve job and find the reason your belt broke to begin with. It is impossible that a valve did not get hit

Find another mechanic. you got ripped off. A broken crank does not mean you cant check the valves. Called a leak down test. This engine should have been replaced. And probably still should. Your talking about a $1500.00 job.

It is common for issues to come from any of the driven shaft bearings.
I mean to say -If the water pump fails.If the idler bearing fails.If the tensioner bearing fails - which is common - for peopleto not change ... gambling that it seems "alright" - right now - at the point ofreplacing the timing belt.
If the timing belt does snap -
Then every intake valve in the head will become bent.Search for a "good used head" and see how manyof the damaged heads are available with bent valves.
If you are making highway speed - the engine will become destroyed -with piston damage.
If you are more fortunate - the valve work can be done.But the labor and the physical amount of work to getthe job done is long and intense - even for those people who do it regularly. ... and costly. I found a reman head for $750exchange.
There also is galvonic bonding for the head bolts - they becomeelectrically and chemically welded to the alloy block - nearlybreaking off - with the attempt to remove each head bolt.
When they do break - someone with grit has to create theright tool situation to drill, use electric current to break the bondand remove what bolts do break.
What could happen when you ignore the time interval thatVolvo suggests - You could loose your car -You could need to replace your engine.You could wind up buying a Toyota.
The options are unending.

Change the water pump, timing belt, tensioner and idler bearingall at the same time.
The special tools for the Variable camshaft timing are notsuggested just to be suggested. They are needed to accuratelyset the timing for greatest engine efficiency and to keep thehead valves from becoming damaged - after a novice attemptsto install just a replacement timing belt.
Flush the power steering fluid while you have all that mess off
to service the front of the engine.
Ignore it all, and it will go away a tow truck to the salvage yard of your choice ... or wind up paying up over and beyond $3500for repairs that might be possible - if someone is willing to takethe job on for you - other than the dealer.

Volvo recommends for Volvo S80, changing the timing belt every 105,000 miles. Needless to say, they are pretty religious about this now.
The B20, B21, B23, and B230 engines are non-interference engines, meaning that the camshaft can be rotated independently of the crankshaft and no damage will result to the engine. That is, if the timing belt breaks, the valves will not hit the pistons; the engine will simply stop.
On the other hand, the B234 16-valve engines and any of the other Volvo multi valve engines are interference engines. Loss of the timing belt in these engines will result in severe or fatal engine damage.
Your car might be fitted with:
2.8L (VIN 90, 6th & 7th digit, B6284T eng, turbo)
2.9L (VIN 94, 6th & 7th digit, B6294S eng)
To get more information you can download the Owners manual at:
http://new.volvocars.com/ownersdocs/2001/2001_s80/01s80_08b.htm

just put a compression gauge on each cylinder that will let you know if engine has a bent valve, gauges are relatively cheap. if the belt didn't have anything to do with your timing belt i doubt you have a bent valve, any check engine light? do you have spark? fuel pump turning on when key is turned to on position?

if it ran ok before the work its not going to be good,start over check all marks the see if you bent any valve by doing a compression test,does it fife? does it have ful pressure