Hello Francesco, welcome to the forum!
I can not pass the level 37 because the number of the diamonds is less than the goal.
Let's have a look:
- the goal (number of gems to be collected to solve the level) is set to 30
- there are three bugs in the level
- each bug creates eight emeralds and one diamond
- an emerald has the value "1"
- a diamond has the value "3"
- the maximum number of gems is 3 * (8 * 1 + 1 * 3) == 33
I try to kill the bugs but they generate a short of diamonds.
Each killed bug gives 10 gems in this level (11 - 1, because the bug has to be killed by touching it with the "deadly shield" activated, to there is one gem less than the maximum per bug), so you can get exactly 30 gems in this level.
You have to snap one field next to the bug to let it move away from the wall, to let it create the maximum possible number of gems. ("Snapping" was introduced and explained in the envelope in level 12.)
If all else fails, watch the solution tape: Go to the main menu, blindly type ":insert-solution-tape" or simply ":ist" (without the quotes) and press "play" on the tape recorder!
