If they are damaged, you will need to take off the cylinder head. You will then have to test all the valves, remove any bent or broken ones, maybe remove the guides for those valves as a bent valve can cause more damage. You will need a good toolkit including a valve spring compressor.
You will then need (at least) to buy new valves and grind(lap) them in to fit the seats. Refitting with new gaskets etc is usually a reversal of removal, but getting the head bolt sequence, torques and valve timing just right is crucial, so a good workshop manual is vital.
The valves are bent..no two ways about it. The head needs to come off and the intake valves all need to be replaced. The exhaust valves should also be taken out and spun in a drill to determine if any of them wobble because of being bent too. Because you speak of "opening the engine" to fix it yourself it's obvious you don't have a clue or chance in hell to do this yourself! Be a shame to see you mess with it and then bend the valves again. How many timing belts have you replaced?!!!
when you have a broken timing belt it nearly always results in the valve stems becoming bent, and in extreme cases the valve heads shear off. (the fiat punto is reckoned to be the only safe engine against this kind of damage),
you do not lap the valves in you discard the bent ones, and fit new ones, or better still buy a complete set, have the valve seats cut, and test the new valves for eccentricity with engineers blue, facing the new valves if necessary, then you can lap the new valves in, and check the fit with engineers blue.
pull the head and check the valves ! if they are bent then take the head to a machine shop and have new valves put in and new valve seals ! you will need a new head gasket and a new timing belt along with a oil change !
A 2012 vehicle I don't think it has a timing belt probably a timing chain.
my timing belt has been broken while driving does the valves are bent or not what is the procedure required to open the engine in home and grind them and reassemble the parts again does will work again .
