"How can we extend the roof to cover top and all the way to the side front as we don’t want flat roof."
If you're dead set against a flat roof then it will be more expensive. I think that a flat roof would work well in this situation but I'm not you.
I think probably the way to make that work would be to have the ridge of the extension running at 90 degrees to the existing ridge line.
Attached is a photo of a chalet bungalow with an extension to the side. It is a chalet bungalow so it has an upstairs but this will give you an idea of what I mean.
This is a lot more expensive than a flat roof.
•First thing is,make the kitchen bigger, kitchen and dinner without using the space from living room?
•Add extra room for study without using the space from existing rooms?
As to they layout, I have a couple of ideas.
In the first one it will mean losing a bit of space from bedroom 1.
Create a corridor (shown in red) that takes some space from Bedroom 1. This links to the garage which becomes Bedroom 4.
Then extend the kitchen (shown in green) to create a larger L shaped kitchen/diner
The second idea is to create a corridor (shown in red) where the bathroom currently is so that no room is lost from Bedroom 1.
The bathroom is moved (shown in yellow) and takes up half of the existing kitchen. The kitchen/diner (shown in green) is now L shaped and the garage becomes Bedroom 4
[EDIT]
"Can we get planning for this tho?"
You don't need planning permission for this, it comes under permitted development.
Although you will need to go through the Party Wall Act process as you will be building right up to the boundary.