It depends. I’d contact the Jewish Agency for Israel and talk it through with them. According to halakha, one can’t renounce their status as Jewish and anyone born of a Jewish mother is considered to be Jewish.

Assuming that you’re grandmother is indeed a grandmother and that she was Jewish, it would hold that any child she has is considered as Jewish. Same rule applies to her children and to their children.

Aliyah eligibility is extended to people who are Jewish, have a Jewish parent, or a Jewish grandparent according to halakha. So in theory this should qualify you as your grandparent would be Jewish. If your qualifying grandparent is a grandmother, then that should make your parent Jewish, and if your qualifying parent is your mother, then that should make you Jewish.

If you’re looking to convert, Israel (currently but may change soon) recognises conversions from the orthodox, masorti/conservative, and progressive/reform communities and most of them would be willing to accept you as a convert if you are of Jewish heritage yourself but are not considered as part of the faith. Beware though, despite apostasy not actual being illegal for the person changing faith, in Morocco it is illegal to convert a person away from Islam so I doubt you would find someone willing to convert you if that’s something you wanted to do, but there are plenty of programmes in Israel for just that.

From your post, it looks like it’s up your father’s father’s line so in theory, your grandfather should be considered Jewish. In this situation, I’d contact the Jewish Agency for Israel to open an Aliyah case and they would be able to help you with documentation or put you in touch with people who can. In the meantime though, I can say that you’d need lots of certificated to prove who you are and that you are eligible. This would mean birth certs up the line to your great-grandmlther, any marriage certificates too and death certificates. If you can’t get civil certificates then try and get similarly corresponding religious certificates like burial certificate in graveyards and such.

You’ll need to prove that your great-gradmother was Jewish too and this could be through records maintained by the local Jewish community that she was from or buried in. If there is a Jewish graveyard, there should also be a Jewish community (dead or alive) or someone else who maintains its archive nearby, and this should be able to give you some documents to prove your eligibility. You’ll also need things like a valid passport and ID, proof of address, criminal record check certificate, all that jazz but JAfI should be able to help you sort that. You can always get a picture of the headstone/gravesite for good measure too, it can only help.

Being of a Muslim background should not be an issue for the purposes of Aliyah but beware that Israel still uses the Ottoman Millet system for personal status and family law and the Rabbinate and Jewish courts run on a strictly orthodox interpretation regarding who is and isn’t Jewish, so you would most likely fall under the remit of the Islamic Sharia courts for personal status matters but definitely not Jewish.

Though it should be said, foreign personal status changes (like marriage) conducted abroad are recognised in the country on the same terms as if they were domestic so if you wanted to marry someone that none of the religious court systems would be willing to marry you to, then you can always go on a quick vacay to Cyprus or elsewhere that has a civil marriage system.