I just want to know how to model this? I was tried but didn't find any way to make it x(.
You can model only one segment of a pattern then repeat it on x and y axis with array modifiers.
If you need a repeating pattern on complex object try tissue plugin
Here is fast preview of the workflow, you just create some planes make some loop cuts move edges up and down
add array modifiers to see the pattern, add more planes, then increase array count and add solidify modifier, you can always adjust or modify your main object later...