Sure definite fix is 1- fix curtain, at top, least 10cm away from bathtub, that is not straight up. 2- seam at bottom of curtain must be 1-1.5 cm. Fill seam with clean washed sand, as weights. washed sand available from builders supplies and look for a broken bag, U only need ‘bout 200 gms, if that+1 They're good!
EDIT- Just noticed your post about toilet proximity. Can you hang the bowed rod higher up? The curtain will still tuck inside the tub, so you won't be losing any real-estate outside the tub near the bottom.