MrPernickety“what the bold part of the sentence means precisely?”
It's like going
through a tunnel. You go in one side, and you keep going
through it, and eventually you come
out the other side. The tunnel image (or anything similar) can be used to see the metaphor that is intended. In English,
to go through (meaning
endure) is used for difficulties of various kinds.
There was a blizzard, and all the roads were blocked. You wouldn't believe what we had to go through to get here! [what difficulties we had to endure]
be through can be taken as a variant of go through in this specific case. Adding and out the other side calls our attention to the fact go through is in itself metaphoric.
CJ