The area around the tub must be caulked not grouted, grout will never hold up, it will always crack. Remove all the grout, clean/prep the surface, and caulk around the tub area...

To expand on GN Builders LLC, all changes in plane should (and really required) to be silicone caulk, not grout for this exact reason as walls and floors move (expand and contract) at different rates then

And the silicone caulk comes in all the colors so don’t accept white for that vertical corner - it will stand out like a sore thumb. The dark grey you have now is available in a matching silicone caulk. And get someone who is good at applying it right the first time - because you can’t go over it once it’s done.

Obviously remove every bit of old caulking and residue. Make both sure tile and tub are clean and dry.

‼️IMPORTANT‼️ Be sure to fill up the bathtub before you begin to caulk to allow for expansion between the tile and tub. Keep it filled until you complete caulking. The water alone weighs approx 330 lbs. 🔹Do not use harsh cleaning supplies. Use Mr Clean or Spic n Span for general cleaning. From time to time, I use a steamer cleaner for deep cleaning.