A layer of ice is bulding on the freezer floor, gets thicker in a few days. what's the problem? I have pulled off the back, removed all ice, and reduced the amount of items in freezer, but ice is building from the bottom again.

The water most likely is coming from a defrost drain blockage. Unplug and remove the rear panel inside the back wall of the freezer. See panel location #4 in the photo=> HERE
You will need to get that panel out of the way to see and clean out the defrost drain.

Click Here=>Leaking Refrigerators
I am here should have questions, Thanks John Tripp Appliance 911

Your drain plug within the evap area of the freezer is frozen, turn frig off, let sit for day or two with doors open. Once all ice has melted then take rear freezer evap cover off and pour water into try and make sure it drains, if not then unplug drain. This is usually caused by a defrost heater bad or unit not going into defrost when it's supposed to, may be main board.

Here I am going to give you a lot of information. Because of the leaking your defrost condensate drain is most likely the reason. All on the page below may not be for your situation and some refrigerators do this over a period of time and the the water has no were to go but the freezer during defrost. Click on link below, Thanks, Sea Breeze
HOW TO FIX A LEAKING REFRIGERATOR OR FREEZER

Your defrost drain line is frozen over.Remove everything from the fridge and turn it off for 24 hours with the doors standing open.
The drain line will thaw and you will return to normal operation.
You could also turn the fridge off, remove the freezer floor panel and back panel. Take a hair dryer and thaw out the drain hole. Takes about 2 hours.
You decide which procedure to use.

You have a clogged drain. If you have a top mounted freezer you might have the drain line on the outside of the fridge. Look for a tube that is thicker than the water intake line and goes from back of bottom of freezer down into the back of the unit to a drain pan. Remove that tube and take it outside and use your hose to shoot a stream of water to clean it out.
If you have a side by side fridge, your drain is still at the lowest point at the rear of your freezer. You may have to removed the rear wall of the freezer to get at it. Remove the back cover to get at the other end of the drain tube. It needs to be cleaned out also.

top part has lost all temp

The drain is plugged. This fridge will defrost every 8 hrs or so. When it does , it will melt the frost that has built up on the evaporator. This melted frost will run down a drain under the evaporator to a drain in the bottom directly under the evaporator. When the drain gets plugged the water cannot drain out of the freezer compartment. After several defrost cycles the melted frost will overflow onto the freezer floor. When the fridge starts back up it will freez this water is the bottom of the fridge. sometimes this water that is now ice will melt on the next defrost cycle and actually run out into the floor. You will have to unplug the fridge or turn it off, then remove the cover to the evaporator. Get a hair dryer and melt the ice aruond the evaporator and drain. Once the ice is removed, check the drain and try to clear it. Once clear, replace everything but the shelves. Plug the fridge back in or turn it back on. Observe and listen for the evaporator fan. It should be running now. When working on the ice on the evaporator always be carefull. The defrost heater can be damaged if up push or pull on it too much.

HI thanks for your question. yes that drainage hole must be cleared. unplug fridge for at least 24 hrs, pull fridge from the wall. remove back plate. clean all coils. locate the drain tube by the drain tray. put a small hose up the drain tube and blow to clear the debris. thanks the appliance doc. please rate my answer. thanks

a frozen defrost drain pull the back panel in the freezer section see if the drain hole is stopped up after clearing the ice