Chinese Sentences 6 (with grammar structure question)

we can go to the lake! 我们可以去在湖辺泊!

I am cooking right now! 我现正在做饭! This is because you have an interogation mark.  If you don't have it, using 現在 suits the nuance.
I am going to cook now! 我要去做饭了!  Correct nuance :)
I am about to go cooking! 我待会儿正在想要做饭! Without 想, it becomes, "I want to COOK now!"  The想 here is equivalent to "about"
because I like to cook. 因为我喜欢做饭.
because I love you a lot. 因为我非常爱你.
but I like to eat dark chocolate. 可但是我喜欢吃的黑巧克力. The use of 但 is for great constrast.  可是 in this case does not mean "can" but a milder form of 但.  In English, there is only one shade of "but"
but I have to go to the bathroom. 但是我要去洗手间 here 但 implies urgency.
if we have time we can go there. 我们可以去那里如果我们有时间, 我们可以去那辺/儿

if you want to we can go there.我们要去那里如果你想/ 如果你想要, 我们可以去那辺/儿里

Here I am not sure how to structure the sentence properly can you tell me which one sounds more native or is there even
another way to say it?

In standard Chinese, 那里 do not really mean "there".  It means "where".  I don't know about usage as in a dialect.  你去那里/儿 means "where are you going?" and does not mean "you go there" (你去那边).

As for 那儿, there are two tones for 那.  The higher tone means "there", the lower tone means "where"

If someone is thanking you profusely, you may say 那里的話 (literally "where do such words come from") or  "speak not of such thanks", or 那里, 那里 as a more intimate way of showing self humility.

It can also use as in a derogatory situation, 那里来的东西 (literally, "where do this thing come from).  In English it is translated as "where did this creature come from" , referring to a person

Chinese Sentences 6 (with grammar structure question)

Chinese Sentences 6 (with grammar structure question)

do you want to go there? --> 你想要去那里吗?
do you want to go to the lake? 你想要去到湖泊湖边吗? You can not go into the lake, so you walk around the lake 湖边 : at the edge of lake.
we can go there! 我们可以去那里!
we can go to the lake! 我们可以去湖边在湖泊!
I am cooking right now! 我现在做饭!
I am going to cook now! 我要去做饭了!
I am about to go cooking! 我待会儿做饭!
because I like to cook. 因为我喜欢做饭.
because I love you a lot. 因为我非常爱你.
but I like to eat dark chocolate. 但我喜欢吃的黑巧克力.
but I have to go to the bathroom. 但我要去洗手间
if we have time we can go there. 我们可以去那里如果我们有时间的话

an expression : 如果...的话，就...

if you want to we can go there.我们要去那里如果你想的话/ 如果你想我们可以去那里
Here I am not sure how to structure the sentence properly can you tell me which one sounds more native or is there even
another way to say it?

Your chinese is really good ! 

Chinese Sentences 6 (with grammar structure question)

You  did this very well,it will be much better if you pay more attention to details.I suggest that you watch some Chinese movies and TV series that you like,it might help you out.

Chinese Sentences 6 (with grammar structure question)