timing specficaions for an opel monza 1989 1600

Hi my moms got the above car and i cant seem to find out what the timing should be. My father passed away and did all this stuff so im trying to take over, if you could help please

the car sometimes starts no problem then it will like Ha Ha Ha and then start then other times the car does that and after a few minutes starts if not then a push start it - people so it could be timing is incorrect or the armiche in the starter that needs replacing i wish to try the timing first as replaceing the armiche could cost money i Guess

Kind Regards
George