Diary - Since I was sick, I hasn't had my Japanese class for three weeks.

[Maybo]

This is an entry from my diary. Please check it and correct any mistakes.

Since I was sick, I hasn't had my Japanese class for three weeks. Therefore, I'm doing some revisions, and I've found I've forgotten half of what I've learnt, especially dates and numbers. It's hard to retrieve the things I learned after a long period of time. I'll have some Japanese classes next week. However, I've decided to learn by myself after the classes.

 

[teechar]

Since I was sick,

That means "because I was sick". You should say "Since I fell ill" or "Since I got sick".

I hasn't had my Japanese class for three weeks.

Always go over your own writing before submitting it. That's how you can catch and correct silly mistakes like that one.
Note also that when we give a period of time (in this case "three weeks", we use "for", not "since").

Therefore, I'm doing some revisions,

"revision" is uncountable in that sense (a student revising a course of study).

and I've found I've forgotten half of what I've learnt, especially dates and numbers. It's I find it hard to retrieve recall the things I learned after a long ago. period of time. I'll have some Japanese classes next week. However, I've decided to also study learn by myself after the class. es.

 

[Maybo]

That means "because I was sick". You should say "Since I fell ill" or "Since I got sick".

Yes, I mean “because I was sick”.

 

[Maybo]

After finishing the classes next week, I won’t learn with a teacher anymore, and I’ll learn by myself.

 

[teechar]

Yes, I mean “because I was sick”.

Then say: "Because I've been sick, I haven't had (any) Japanese classes for three weeks".

After finishing the classes next week, I won’t learn with a teacher anymore; and I’ll (just) learn by myself.

You can change the last "learn" to "study" if you want, to avoid repeating "learn".

 

[Maybo]

Because I've been sick

But I’ve recovered now.

 

[Maybo]

Can I say “Because I was sick three weeks ago, I haven’t had Japanese classes since?

I think I recovered a few days ago but I still wanted to rest so I haven’t had classes for three weeks.

 

[Tarheel]

Can I say “Because I was sick three weeks ago, I haven’t had Japanese classes since?

That works.

I think I recovered a few days ago but I still wanted to rest so I haven’t had classes for three weeks.

That's a compound sentence. Where should the commas go?

 

[Maybo]

That works.

That's a compound sentence. Where should the commas go?

Before "so" and "but".

 

[teechar]

Can I say “Because I was sick three weeks ago, I haven’t had Japanese classes since?

Say: "Because I was sick, I haven't had Japanese classes for three weeks".
"I was sick three weeks ago" is slightly different. It suggests the illness was shorter.