Actually, I wanted to clean my room in last month.

Because, cleaning the house before the new year is a custom in Japan.

It would be better to connect this sentence with the previous one, and not start a new sentence with "because".

We clean the house to invite gGod ofto the year.

But I had plan that arened to meet my friends and go to my parent’s house at the end of year so I can’ouldn't clean my house.

Maybe God did not come to my house…But I want to start the new year in a clear room so I cleaned my room today.

Actually, I wanted to clean my room in last month.¶

Because, cleaning house before nNew yYear's is a custom in Japan.

We clean the house to invite god of year.

We clean the house for the kami(Shinto Spirits).

But I had plans that areo meet my friends and go to my parent’s house the end of year, so I can’ouldn't clean my house.

Maybe Godthe spirits did no'nt come to my house…But I wanted to start nthe New yYear in a clearn room, so I cleaned my room today.

Actually, I wanted to clean my room in last month.

You don't need in :)

Because, cCleaning the house before new year is custom in Japan.

You don't need because, it's simply a statement

We clean the house to invite the good of new year. ?

I'm not sure what you were aiming for in this sentence

But I hadn't plan that arened to meet my friends and go to my parent’s house at the end of year so I can’t clean my house.

Is this what you mean?

Maybe God did not come to my house…But I wanted to start new the year in clearn room so I cleaned my room today.