Hi, I have removed the old shower tiles and the surface has the old thin set on the floor in spots. I also, took some of the mortar out with the old tiles. Do I need to resurface the floor with new mortar and fill in the low spots and smooth over before laying the new tiles? This is my first tiling project. Thanks, mike

I would because if the surface isn't flat you may have an uneven floor and that may cause tile cracks and breaking in the long run.