Active job

Retile a leaking shower base

we have a tiled 865square tiled shower, it has a 60mm lip off the floor on the two glass sides. We had it retiled and the black waterproffing redone 2years ago, but it now leaks around the lip part in the grouting we think, as the insurance man said his tester shows the floor under the tiles outside around the shower is damp. Because the shower is partly recessed into the wall, we can not fit a premade shower so need some one who can give good advice and fix it, replace tiles, not sure what. Last guy did not do a very good job as water sits in shower now. Is there a great problem solving tiler who may be able to help. Thanks