How can I makeover my living room (picture below)?

It is pretty and clean! Love the window. To me it needs color! Choose something bright and cheerful and repeat in an odd number around the room. Throws, pillows, lamp, rug, art, etc.

Needs patterns and color . Maybe start with a colorful area rug, add some patterned pillows in same colors, paint the walls a color from your new design.

I would definitely say it needs some colour, its very beautiful and bright, if you wanted to add something on a smaller budget you could add 1 or 2 things of color and add a mirror! I would say a rug, or something on the wall, or even some bright flowers

Yes some color for sure, you could add some colored pillows, colored mats on your pictures, an area rug picking up the same color, maybe even some curtains for the sides of the window - I like the sheers for the brightness. Kitty looks lucky with all your choices.

The room needs additional sources of lighting, in the corners, and at various levels around the whole space.

Every room should ideally have incidental, task, and ambient/accent lighting.

. three kinds of lighting every room should have explained

https://www.thelightbulb.co.uk/resources/3-basic-types-lighting-when-to-use/

Something that immediately strikes me as being 'wrong' with the arrangement is that the area rug is way too small, and is crammed into the corner.

What color do you like? Is the chair in the corner purple? If so and you are keeping it, look for colors which work with it. The window looks undressed. Drapes would look good. The rug is too small. Try pulling it out into the room with just the front legs of the sofa on it. And it appears as if everything is all on one side of the room. The room has nice floors and good natural light to start with.

I would add a pop of color in either the curtains or the rug. Then take accents from that and incorporate it into the pillows and throws