If you haven’t had too much experience at tiling, it’s often easier to cut out all of the tiles and put them in place before you apply any adhesive. So continue cutting the tiles so that their cuts match the lines on the floor and the tiles are following the pattern of the floor. They key to success is patience and to keep following your pattern. If you’re a more experienced tiler, you might want to dry-lay half the tiles and then glue them in. This gives you some flexibility if you need to trim some tiles to fit in the other half of the shower base.