garden shed

Garden shed has been cleaned out. The poor thing is collapsing, the workbench is 2 inches lower at the back than the front;  it never used to be like that! It is over 30 years old, the centre part of the floor has given way, so nailed a board over the gaps for safety. 
The corner in the picture is a good 6 inches lower than it should be, so laid some more boards on top to help level it up a bit, but the trend continues downhill.
I know this is not good structural engineering practice, but the best i could offer. Im sure a carpenter would advise me to stick to my knitting…
Looking at the above I realise some of the problems could be attributed to the owner too – Ha Ha… words such as
poor thing is collapsing…. never used to be like that… centre giving way,  6in  lower than it should be…,and to end it all….. TREND CONTINUES DOWNHILL!