You need a tool called an 'Easy-out". It looks like a drill bit but is tapered and the spirals twist around the the left instead of the right like a drill. There are many sizes so you will need to measure the hole in the bolt and match the hole size to the Easy-out size.
Be sure when you insert the Easy-out into the hole that it doesn't 'bottom' out, i.e., hit the bottom of the hole before it is in far enough to grab the sides of the bolt. If it does bottom out you will either have to go to a larger size or grind off the small end of the Easy-out. Drive the Easy-out in with a hammer until it is tight in the hole. Grab it with a pair of Vice Grips on the flat sides and twist it to the left. Generally things involved with the lubrication system aren't rusted in place and can often be removed easily.
If you are not comfortable doing this kind of mechanical work get a mechanic to do it. I see you are from Columbia. I spent 20 years traveling around the world, I was in Columbia in 1977, and have seen some of the wonders that mechanics in these countries can do. Ask the mechanic how he will get the bolt out first before you let him work on it. If he sounds like he really doesn't know, don't let him experiment on your car. Make sure he has good Easy-outs and not a bunch of broken stubs. If they are broken it means that he probably doesn't know how to use them.
Check also that the part inwhich the bolt is broken might be removable from the car. If it can be removed it will be much easier to repair than if you have to do the work on your back under the car.
Be careful if the mechanic talks about drilling out the bolt. Hollow bolts used in the oil system have very thin walls and it is easy to damage the threads in the bolt hole. If the threads are damaged too badly you may have to insert a 'Heli-coil'. This will restore the threads, but is a big hassle to install. You can live with some thread damage as long as you can tighten the bolt enough to make a good seal.
The seal on hollow bolts come from the two copper washers (be sure to replace them with new ones)on either side of the 'banjo' fitting and not from the threads.