Chrismas Day in Japan

In Japan, many people spend time with their lover, but I don't have one, so I spend with my family at home.

I think that sentence sounds great when you say it, but it's a little weird to read because of all the commas. A possible alternitive is "In Japan, many people spend time with their lover, but I don't have one. Instead, I'm spending it with my family at home.")

Maybe I'll go play tennis?("My part time job friends also..."  Do you mean "My friends from my part time job" or "My friends, who have part time jobs, also..."?) don't have ("lover" -> see note below) so maybe I'll play tennis with one of them."

We don't usually say "lover" unless inferring certain... "intimate activitives" if you catch my drift. Usually it's "girlfriend/boyfriend/husband/wife." "Spouse" is another good word that means "Husband or wife." 

Chrismas day in japan

Christmas day in Japan

In japan,many people spend with lover.but I don't have one.So I spend with my family in my home. 

In Japan, many people spend Christmas with their lovers, but I don't have one so I spent the day with my family at home.

Maybe I go to play tennis.My part time job friends also don't have lover so maybe I play tennis with one.

Maybe I will go and play tennis. My friends from my part-time job also don't have lovers so maybe I will play tennis with one of them.