1) This is using make in the sense to cause something requires either a noun, or a verb without to. For example,
The photograph makes him look about 80
In your sentence, look is the infinitive, and looks is the present simple (3rd person). We want the infinitive, so it is:
I want to make my house look more beautiful
2) If you negate a sentence with be in it, you just put not after the verb:
The ball is red
The ball is not red.
For all other verbs, you put do not in front of the verb:
I want a red ball
I do not want a red ball
The main verb in this sentence is want: the correct sentence is therefore
I don't want you to go there
There are circumstances in which one might want to phrase the wanting in a positive way, for example to emphasize the wanting, but then would be more likely to say
I do want you not to go there.