Well, if it can help, the map looks like that:

There is three bosses at the end and you must fight 2 in a row anyway. The three main spider bosses are weak against Slice. The main true boss is in the middle, just before the Note panel.
Maybe if you buy all the lvl100 red manyu in the shop and waitfor the next blue-red manyu map for level up your Alpinia you will be able to finish this.

Anyway, if it can help you in term of setup I use the default positions with team speed like that:
1: 525
2: 480
3: 539
4: 670
helper: I'm not sure for really fast/slow teams but it seems it's not important.

The 4th team will face the boss on the right and the main boss. Helper will fight the one at the botom.
If you have an ally enough strong (like with full high level 6* team), you can certainly do it by putting all your best units in the Alpinia's team for the boss fight (note that you will certainly fight some random pest on the way).
In the three other teams, use units enough strong to kill the pests.
So, good luck if you want to try it