If you have unlimited time you can try to stir the suspension for days or weeks, then filter out whatever didn't dissolve.

To speed up things you can try to increase temperature, preferably till everything dissolves (assuming your compound is not heat-sensitive). Filter the warm solution. Cool down to room temperature a portion of the clear solution and seed it with a little powder of the original solid in order to form a true saturated solution. Stir for a while (e.g. overnight) and filter. Now analysis of the filtrate will give you the actual solubility of your solid at room temperature.

Next you can make a suspension of a desired concentration close to, but not quite at, saturation. Leave it stirring and go on an extended vacation (or just do something else for a few days).

Another way to speed up the dissolution is to grind the solid powder in a mortar (carefully to prevent losses) under the solvent. This can be useful with relatively large particles, especially gelatinous or sticky ones, and/or if heating is undesirable.

Hello Tsun Yeung Wong

I think the method described in this article could be useful for you.

It involved the encapsulation of a poorly water-soluble drug into nanocarriers, followed by coating with β-cyclodextrin(β-CD), which are cyclic glucose derivatives and considered as pharmaceutical moieties that can generate hydrophilic exterior surface and hydrophobic interior conical cavity.

Article A facile design of smart silica nanocarriers via surface-ini...

Doctor. Try to use ultrasonic bath put sample of your drug using the adequate solvent, try to not surpass the solubility amount of drug inside solution left it in ultrasound bath until it dissolve totally I tried this aspect before it works well