Return before connecting Earth to the Univers!

Zack barely survived during the 6 years after Earth connected with the rest of the Universe. The first 5 years he could do only menial chores for the family as he could do nothing as he was an illegitimate child and his mother died of childbirth. All changed in the fifth year when the initial planet protection ended and Earth was invaded by Sharkdokin. The next year barely suvived with Mike, a soldier, help which he started to date. After dying he woke up with a recall stone (a stone that keeps Mike's memories) and a crumbled gem (Mike's last memento). So the first thing he does is return the recall stone to Mike so he can remember him and start planing his revenge on his family. *I'ts my first novel, so I would prefer some feedback to improve on it.* *English it's not my first language, so if something doesn't make sense make me know and I will try to correct it.*