As stated in previous answers, both are okay to use, but adding "in" is more common, at least in the U.S.

I love the idea of custom package requests by students; however, it is somewhat concerning to have the lesson requests at a set time. While this is convenient and excellent for building habit, it may backfire should the student or teacher's schedule be variable. I would love to see the custom package option in force but without the restriction of set times.

I love watching the movie Spiderman. It is interesting how a spider bites the hand of a man and how everything changes for him afterward.

To make it easier to see corrections, you may want to post this under "Exercises," but I can still help you! Below I will edit what you have written. If you have any questions about the corrections, I am happy to explain. I am against donating any amount of money to charities each month. A few years ago, I saw on the news that the money we had donated to charities at the end of year was not being used properly. Some employees of the company that managed the donated money stole and used the money. Since then, I have been against donating money regularly. If I have people in need around, I think it would be better to go and give money or things for them in person. Just for your reference, the news incident you are referring to is a crime in the United States called embezzlement. There's a new word for you if you didn't know it!

This is the teacher’s lounge. We hung some Xmas decorations on the window pane. There is a large table. You can’t see them in the picture but there are some teachers working on their computers, filling out school reports. There is a small, white fridge in the background. There’s a sink, which has a leaking problem. I’m lying down on the sofa because I was tired of filling out school reports.

You can use the middle one "Just as I heard of this test..." but it is more natural to say "When I heard of this test..." Good question!

In general to carry out the birthday party: you make a cake for it then invite your family, friends, and people who love to come and join. Then you are given gifts from people. You also sing a birthday song and make a wish.