Your temperature looks good.
[COLOR="Blue"]What is the reason to this happening?[/COLOR]
Without being there I cannot say what caused the insulation to get wet.
Once fiberglass gets wet it looses it's insulation value so will have to be replaced.
[COLOR="Blue"]What should I do to correct it.[/COLOR]
Trying to dry fiberglass out is just an exercise in futility. I know this because years ago I tried it and it took hours in a hot oven.
The insulation blanket used by the manufacturer is probably not available so you have the following options. A lot depends on if you can get at the insulation to replace it. This may be a challenge. All I can say about this is a putty knife comes in handy here as trim pieces usually use hidden clips that have to be released in order to take the trim parts off. and then screws hold the liner to the frame.
1. Buy some batt insulation and replace any damp/wet/frozen insulation.
You should be able to peel off the thickness you need. Also do not stuff it in there tightly as that also reduces insulation value. You may even get lucky and find an insulation that is the correct thickness.
2. Use Styrofoam. I am not familiar with European building materials. In North America white Styrofoam is open cell (can absorb water over time) and blue or pink Styrofoam is closed cell (will not absorb water) so the coloured stuff is better but white is still better than fiberglass. It should be tight against the liner so no air can get between it and the liner or you will again have condensation. Any air space should be on the outside towards the metal case. The thickness will depend on the distance between the plastic liner and the metal outside case.
3. Use spray foam. Again I am not sure what is available or if you can get to the area that needs it. See below for what I am familiar with. Pull out the wet fiberglass and then fill the voids with the foam. I would use the window and door type as it expands less than the regular type so will be less likely to warp your plastic liner. It sticks to everything so wear old clothes and latex throw away gloves. Also have paper towels or old rags available. Note that I have never used this on a fridge but have for sealing around doors and windows. It does a good job but is a pain to work with. I make sure to have a small box available because once the foam leaves the can it expands so you release the trigger but the foam in the dispense tube keeps expanding and you have to have some place to get rid of it. Once it has finished expanding cap the end of the tube so it does not set up and block the tube, a bit of tape should do it.Put one pass of foam in then wait for about 15 minutes to let it expand then put in another pass. It actually uses moisture to cure so the area does not have to be perfectly dry. Another problem with it is that I am not sure if it will be compatible with the plastic liner. They should be able to tell you that at the store or it may say on the can. I would check it by putting a little bit on the liner first to see if it will eat the plastic. Do not touch it till it has cured. You can then easily cut off any excess foam. Touching it before it is cured will just get you a gooey hard to clean mess.
With luck you have some experience using this stuff, there are help videos in the below site. Personally I have a love hate relationship with it. Hate using it but love the results.
Spray Foam Insulation | GREAT STUFF? Insulating Foam Sealant[COLOR="Blue"]Is the condenser placed above the insulation?[/COLOR]
If by condenser you mean the compressor it is usually at the bottom back behind a cover. The condenser coils are either also below the freezer compartment or mounted on the back outside of the unit. Both of these are outside of the insulation blanket.
The evaporator (cooling) coils will be inside the freezer. It will either be a separate evaporator or they may be built into the shelves. There is a possibility that the coils are on the outside of the liner but inside the insulation blanket. This is how chest freezers are put together. I have never seen an upright that uses this but as I said I am not familiar with European units.
Looks like my post turned into a novel.
Sorry about that but I am sort of shooting into the dark here and tried to include any info that popped into my head that I thought might be useful to you.
