Thanks for the edit! Sometimes the text doesn't fit in the bubbles, but honestly I don't know how you could have done otherwise since the bubbles are quite tiny. It would be interesting if someone had an idea about how to bypass the problem, since you cannot reduce the text dimensions too much.
Smaller/narrower font. And breaking the words into several lines.
Adapting the text to vertical speech bubbles can be a pain, but I'd prefer smaller font to writing text vertically (one letter above another). It's not that bad here, but often it's totally unreadable.