rainwater coming from inside above the windows in the kitchen

[Maja]

I bought a property in August 2018. A month ago, so far twice during heavy rain and wind, the water started to leak above the kitchen window. There is a small gap between the window and the wall and water is coming through there. I marked this with yellow on the pictures 05 and 06. At first, I thought that I needed to replace the windows and fill the small gaps with a sealant so I called a designer to give me a quote. After he inspected the kitchen and the window from inside and outside he told me that there is nothing wrong with the window itself, but that water is coming from the outside wall somewhere from above. The roof is inspected and there are no leaks in the property above mine. As can be seen on the kitchen ceiling, there is no damp or leak. There were also no damps or leaks previously in the kitchen (see pictures 01 and 02 from 2015 and 04 from 2018). The previous owner has done some work on the outside above the kitchen window (see picture 03 from 2015). I am wondering whatever has been done back then could be botched work and what could be an issue? Lintel, cavity tray? I have no idea how to approach a problem. Should I call a local bricklayer or construction company? What they should repair? Lintel, cavity tray, or should they re-roughcast externally to weatherproof the exterior walls? Overall, the apartment is in very good condition, with no leaks on other windows and no sign of damp. In the beginning, I foolishly believed that I can fix the issue on my own with a little bit of sealant, but I will need an expert. Any help is more than welcome.
IMPORTANT EDIT TO THE POST
I have noticed that the window is not properly sealed from the outside. I was wondering could this be the initial problem? Is it a good idea to seal it with Geocel TheWorks which is an all-purpose sealer and adhesive and afterward paint the outside window walls with water-repellant paint? If this fails, should I check for the faults in the cavity tray?

 

[Maja]

I have been suggested to re-render the outside wall above the window as there is a high probability that the water leaks between the old and new render. It looks like a reasonable suggestion. Should I call the plasterer? The wall is roughcast. Is there any tips and trick while re-rendering?

 

[Rad1o]

I would want to check where exactly the water runs in.
Get someone with a garden hose and jet onto the top of the window to check whether the water is running in above the window. This would be a quicker and cheaper DIY fix with silicone. The seal above the window looks very uneven.

If that is o.k. jet onto the new rendering and again look for water ingress. If this is the source this probably needs rerendering and costs more.

 

[foxhole]

Looks like poor sealant all round window , would not hurt to dig out existing and check condition before resealing, only cost time and tube of sealant .