Terrace floor / garage roof leaking / seal stone floor?!

Hello everyone, just a quick note, I am a complete beginner when it comes to stone/concrete and the like.

Two years ago I inherited my parents' house and now I am clearing out the garage and so on.

The problem is, the terrace floor, meaning the garage roof, has always been or has been for a very long time somewhat "leaky."
So that occasionally in winter, when it has rained for days, some water has dripped into the garage.
My father had taken some measures back then, such as pressing silicone into the cracks between the stones, roofing felt, etc.
All somewhat successful but nothing permanent.
The current situation is roofing felt over the terrace slabs and wooden boards on top.
The wooden boards will now be removed because they are already completely rotten, brittle, and ruined.


Under the wooden boards is, as you can see, the roofing felt which is apparently leaky here and there, and underneath are stone slabs.



These were apparently painted brown at some point because originally they had a different color.

So my plan now is to remove all that stuff on top (wood and roofing felt) and then coat the stones with some kind of (insulation) or liquid silicone, sealing compound or whatever, and then eventually put a topcoat on with a floor made of possibly 2-3 layers.

Now I need your help, which material I should use for what.. The internet is full of everything, but as a clueless person I don't want to just buy a pig in a poke and have to redo everything after a year. So it should be done properly.

Can you give me tips on what to buy?? I am thankful for every tip, here are a few more pictures.

Hello timyvr6, You should first remove the old structure, meaning the old wood and the roofing felt. Sweep the area with a steel brush (can be rented). Now let the area dry thoroughly. So it will be a job for spring. Paint the dust-free, dry area with cold coating (available at the hardware store) and let it dry for 1-2 days. Then 2 layers of welding membrane are welded on. The first layer as the base membrane, the second as the upper membrane. Please make sure that the seams lie neatly on top of each other and are properly welded. At the edges, of course, lead slightly upwards. Then the roof should be watertight. However, the welding membranes are not permanently walkable. If this is desired again, an additional structure is required.