Do I need to lubricate the bolts or they should be dry because when I was trying to tight the last 90 degree it was very hard and I was afraid that the bolts would snap so I tightened all the bolts 70 Nm.
I take it you are on about head bolts? It will say in a manual with whatever sort of motor you have whether they are fitted dry or wet,a lot of head bolts are stretch bolts,ie use once and replace but one thing to check is to make sure there is no oil sitting at the bottom of the threads in the block or you could get hydraulicing and never get a true torque setting with the bolts.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.