Decorators caulk and some paint to match current paint.
Scrape out existing stuff and replace.
Yeah I’ll give it a shot. I’ll get the tools tomorrowIt's pretty cheap if you need to buy some. Just get screwfix no nonsense stuff and give it a go. You will need a silicone gun too.
I can only assume you are young and venturing out so it's good that you have enough care to spruce the place up.
YouTube is your friend for most DIY stuff.