I can’t see the measurements otherwise I would change this.
It seems to me the ratio is wrong and the bedroom should be narrower and the living space bigger.
The flow is wrong :- the front door should be positioned on the right to change the porch from a walkway to the front door and into a small but useable outside space, putting the plumbing for the kitchen and bathroom together is economical.

So consider what is things are fixed because of the building……. Perhaps you already have a soil pipe in the left hand corner or a downstairs boiler?
But perhaps there are some things that are not set in stone for instance window positions, having a long narrow porch.

You should also think about if there are any requirements for whoever is going to use it….. do they need a washing machine or outside storage for instance?

You might also think about how windows will line up with whatever is downstairs so externally it looks ok. Ideally you wouldn’t have one window half in the shower or another right behind the bed.
Additionally this seems to adjoin another building near the planned front door. It’s that other building tall and will it make the porch outside that bit of front door dark and useless?

One option

Hi Jonathan,

Thank you for the suggestions you provided.

The place is about 25 square meters so we rearranged the layout but we will ensure we have storage too.

I’m confused. As you stated it was an extension it suggested the space was not built.
If it is already constructed you will have existing windows and water supply and drains which will dictate where things can go.

Please explain where everything is. If this is an existing building a photo of the exterior will help get more comments in this forum,