Hello I am fairly new to the the whole DIY stuffs and since I don't live in that house anymore I do not have a picture of the problem. I did search online for the issue but all of them has the American toilet model (which has the out pipe under the toilet) which is different that mine and I already have a solution to fix it.
The actual problem I am facing is the screws aren't helps and the material which places the toilet in place is now dissolved or missing. I would like to know are there any kind of fills or material (other than cement) which I can use to fill the gap of the toilet and the ground to hold it firm. I thought of Gypsum Plaster but found out they are not good for moist area. Hope I conveyed the problem somewhat comprehensively. English isn't my first language so apologies for the clarity.
This is roughly what I meant by the different design, as you can see the outflow pipe in attached with a sort of wall mount.