Thank you guys!
I'm sorry, this update would be a bit longer.
On weekend I did a bit of work.
I have borrowed tile cutters from my girlfriend's dad:
My take on cutting uneven sides from wall.
Flip the tile, use spacers from wall:
Use another spacer to mark line:
Same on other side.
Align one mark against cutting wheel:
Align other mark against zero mark:
Done:
And maybe this is common knowledge

Anyway, cut first two sides:
Laid:
Other two cut:
Laid:
Cut sidewalls:
Laid sidewalls:
Cut tops:
And some work from today.
I have finished hole in the corner of room.
Some gravel to level the bottom:
Taking measurements how much to cut:
Tube end would be resting on tile on the bottom:
Cut marked:
Cut with universal disc on angle grinder's lowest speed :
Marked cuts for water:
Cut again:
Aftermath on me:
Cuts for water in tube from inside:
Covered, so I don't get any gravel inside when I would be filling the hole around it:
Placed in hole:
Hole filled with gravel and compacted:
Rest filled with concrete:
And I have laid tiles on tops of the step:
I still have a few tricky places to lay and then finally grounting.
My knees are totaly gone

Stay tuned for more!