How to seal a conduit with an underground cable?

I am not afraid of the future, the 3x2.5mm cable will definitely be sufficient for us, we just want to connect small devices to the sockets.

I only thought of the conduit so that it can be replaced in the future if it should ever break, for example if it is hit with a spade or something similar or if an animal gnaws the cable or something like that.

After we have laid the conduit/cable, we will then have part of it paved over directly and it would no longer be so easy to get to it.

I only thought of the empty conduit so that it can be replaced in the future,

But then you also have to provide a pulling wire for a new cable, etc.

I am not afraid of the future, the 3x2.5mm cable will definitely be enough for us, we just want to connect small things to the sockets.

I only thought of the empty conduit so that it can be replaced in the future if it should ever break, for example if it is hit with a spade or something similar, or if an animal gnaws on the cable or something like that.

After we lay down the empty conduit/cable, we will have part of it paved over immediately, and it wouldn't be so easy to get to anymore.

If you pave over it, you don't need to be afraid of hitting that part with the spade. But for that, there are plastic strips in different colors (I don't know exactly what they are called) that you put in when backfilling, a little more than spade's height above the cable. If you ever dig there, you hit the strip and know that the cable is there.

I also laid 3x 2.5 earth cables in a conduit under the pavement. Maybe not necessary, but it doesn't really matter for the 15.-. No sealing is needed at the front or back…

That's called a warning tape for routes. But it only helps if the excavator driver knows that there is a route there and digs carefully until he has the tape on the bucket and/or a stupid... uh colleague with the bucket is standing in the trench and poking carefully.

Empty conduit is used to be able to easily pull something through later. You don't necessarily need a pull wire for that, a "cable snake" can also work in most cases, sometimes even better than a "pull wire". If a LiYCY was pulled in over 30, 40 meters, as electricians like to do, it will simply tear with a bit of resistance in case of doubt... and then you stand there looking silly...

Underground cable, i.e. NYY for the NSHV area or the corresponding equivalent for >1kV, any professional company will just throw it into the ground without a protective conduit, because the cable is exactly designed for that...

Different topic: If an NYY is laid in a protective conduit, you should also bother to deal with the current-carrying capacity. It then doesn’t necessarily have to be 16A for 1.5² anymore. Soil cools (at a certain laying depth), empty conduit insulates because of air...

Thank you for your answers

Doesn't it always make sense to lay the cable in a conduit?

We want to lay underground cable NYY-J 3x2.5 mm² because we have about 25m distance

Would you lay the cable without a conduit? I thought it definitely makes sense so that you can replace the cable if necessary (in case it gets damaged by something) e.g. water, shovel, or other things

Without a conduit, we can't easily replace the part that is paved anymore
Another part of the cable goes through the flower bed

Conduit M25 costs €50 for 50m

Would you just leave the end open and let water and dirt get in?