Please can someone solve this and put my mind at ease?

R2C2 should be a square with two lines in front, you could think of it as the same figure seen from a different angle undergoing the same proccess

Hello! I can only see 3 solutions:

1) From R1C1 you find R1C2 and the same process for R2C1 -> R2C2. In R1 we observe that one from line is missing (going from R1C1 -> R1C2). Using the same thought process we see that R2C2 just misses one front line compared to R2C1 (whichever you want).

2) We can go from R1C1 -> R2C1 and see that it's just mirrored, as @piquon already says! So, similarly from R1C2 -> R2C2 we can just conclude it'll be mirrored, so it's a square with 2 front lines.

3) The third solution I can see it's weird. We can go diagonally. For example from R1C2 -> R2C1 and we observe that the 2 lines that already has behind the square, come in front and 1 line is added at the back. Using the same process from R1C1 -> R2C2 we conclude that the 2 lines from the back come in front of the square and then: either the 1 in front stays there and 1 new line is added at the back (so we have 3 in front and 1 new at the back), or the 2 come in front the 1 line goes at the back and 1 new comes at the back (so we have 2 in front and 2 at the back).

I cannot see anything else, and by not having multiple choice options we can squeeze every possible scenario! Hope that my reply will be helpful.