Tonight's class was on the different sensations between males and females when they are having sex.

Since you are talking about multiple different sensations, I would use the plural. Also, since you are discussing general sex between many men and women, I would use the plurals for them as well. Alternatively, you could say "between a male and a female," and the sentence would be correct, but without either "a" before or "s" on the end, the sentence sounds a little awkward.

PThe professor of this course is an extremely humourous and lovely old guy.

You need the article "the" because you are speaking about a specific.

"Humor" is a noun and sounds wrong in this situation. Instead I would use the adjective "humorous."

He has been encouraging us to participate into his class actively since the first lesson.

"In" would be the correct preposition to use in this phrase. "Into" is use to communicate movement, but "in" is used for many more situations.

In China, we students often keep silent while teachers are blatthering on the platforat a podium, and he always complains about that.

I have never heard the word "blatter" used before, although according to a dictionary you have used it correctly. I am guessing you instead meant to use the word "blather" which is much more common.

"Platform" is a little unclear in this situation, so you probably would want to use a more specific word like "podium."

Every time we came back down into silence, he would stopped his lecture and grumbled "I'm the only one talking again.".

"Every time" is two words, not one.

"Came back down into silence" isn't a common phrase and instead I would say "returned to silence" or "became silent."

Even though you are talking about something in the past, since you used the word "would," you need to pair it with "stop" and "grumble" instead of "stopped" and "grumbled."

The period always goes inside the quotes, not outside the quotes. No need for a second one.

It's an effective way to gain our hotenergetic respondses because we were always wantinged him to continue his lecture.

Hot doesn't have the right connotations for what you a trying to convey, and instead I would suggest "energetic."

It sounds more natural to describe this action as completed in the past with "wanted,' than as ongoing in the past, with "were wanting."

The content of this lecture was very straightforward, which contain and covers many aspects of sexuality, such as '"How many times per week is good for health' ?"and '"Different types of sexual position'.s?"

Which isn't the the right word because you aren't tacking on a little bit of unnecessary info at the end.

Covers sounds more natural than contains in this context.

Use quotation marks (") instead of apostrophes (') when quoting someone.

When quoting a question, put a question mark at the end of the quote.

Since there are multiple sexual positions, you would say "positions."

This course really change my thoughts on sex.

It sounds more natural to use the plural, because more than one of your thoughts have been changed.

People always think this cannot be put on the tablediscussed openly and refuse to teach children about sex.

"Put on the table" isn't a common phrase for this context. Instead you could say it more literally with "discussed openly."

But it's just theat very lack of knowledge on sex that put many children at risk.

It sounds more natural to use the word "that" instead of "the" because you are referring back to something you discussed last sentence.