The problem about the wood shelf for work

The problem of wood shelf:

When I was making the gap, I match the acrylic sheet and fit the gap,but the sheet is still flexible. So I want to make the acrylic shelves attach to wood board very tight and insect the sheets, because I am afraid if the sheets are flexible, it will make ceramics fall down. But I thought If I use sandpaper, I can sand it wider and fit the sheet perfect. However, the sand paper doesn't work very well. And the wood glue has already glue the two boards.

I spent a whole day to sand the gap but still cannot insect the board. After I painted white, some width of lines on the wood board is much more narrow, so the acrylic sheets are longer than the board. So I cannot insect the acrylic sheets inside. In this situation, I totally cannot use the wood shelf. Only way I can do is put on the table, although it is not my imagination. I feel very depressed that I spent most of time on making but failed. This is the way I can learn. I am not familiar with wood workshop, so I didn't arrange the wood shelves very well. Next time I need to leave more time on wood structure and be more familiar with the installation for exhibition. I will be more responsible for my work!