thank you for your answer and your help, sir!
The picture you posted shows an overview of android projects. In the iOS version of thunkable, there is no trash can beneath a download button.
In the iOS version, there is no possibility to download project.
In the iOS version, there is no delete all blocks button after a right click in blocks section.
You may understand, that I am very grateful for you help, but do not really understand the link between my problem and the issue you posted in this thread.
Besides that, thank you for letting a member of the developers team know!
BTW: when i open my project now, all blocks, which were originally on screen2, are now on Screen1(where the bunch of blocks were deleted), Screen2 is empty, although I made noch changes there. This is strange, because the blocks now on Screen1 have references to labels and images, which are not on this screen