Hi,
Can't find any info on your model but are there any oily patches around the compressor or condenser coils?
If so this could indicate a refrigerant leak.
If there are no signs of a leak it could also be a faulty compressor or a blockage in the sealed system but you would need the appropriate equipment and possibly the necessary licence (environment regulations in your location may state licence required when working with refrigerants) to test the sealed system pressures to identify what and where the problem is
How old is the freezer?
Most refrigerator manufacturers offer a 5, 7 or even sometimes a 10 year parts only warranty on the sealed system but only 12 months on the other refrigerator components. The sealed system includes the compressor, evaporator unit, condenser unit and associated pipes etc. This may be the same for freezer manufacturers.
Check the freezer’s user manual for the warranty statement to see what is covered. It may be that if it is a fault in the sealed system you may be able to get it fixed more cheaply under warranty, especially if it turns out to be the compressor that is the problem.