Tile grout blown, tiles easily lifted up. what's the problem?

[Bond]

another issue is that the tiles slope downwards as they approach the front door!
how would i straighten this? is screed the correct material?
Thank you!

If you are lifting and replacing the flooring, you can level the floor by fixing timber fillets onto the joists. ( tapering timber pieces, to bring floor to level ,before re-laying flooring).

You say that you have damp , half way up walls. Also worth checking the condition of the over site, (is it sealed). What is the sub floor ventilation like?. Do you have issues of sub-floor condensation. Closely inspect joist ends where close to damp external walls.

 

[Time's Ran Out]

But all these issues should have been addressed by your tiler on inspection before he attempted to lay tiles.

 

[Flintstone]

Your best bet is to get a genuinely good tiler in who knows what's what to sort it all out for you, pay him well and put it down to experience

 

[ATZ Tiling]

Most self levelling have Gypsum in them, so you will need to check for damp prior as this would likely fail too.