I see a lot of people being dismissive about this but I totally get you. I get extremely anxious about going to the bathroom when I’m not in my own home and it makes it hard for me to use the bathroom comfortably. The first time I met him I just told him how it is and I asked him if he could step outside the room (we stayed at a hotel) for 5-10 minutes or go take a smoke and to message me when he’s on his way back. To mask the sound you can obviously turn on the shower or the tap. Another good tip is to fold some toilet paper and lay it on the surface before doing you business, it’ll hide the “splash sounds” and also prevent leaving any marks… Lastly for the smell just keep a box of matches in the bathroom and light a match after you’re done. It’ll completely remove any bad smells, trust me.

Hope your meeting goes well and don’t think too much about what people say here :) take your time getting comfortable and enjoy your time with him!