Page 27: I don't speak Japanese, but I think when Gotanda said "speak the way you normally are", he probably meant "speak the way you truly are", or "speak the way you truly feel".
The way she normally speaks is performative, and is measured to get a specific response from people. That was what Gotanda has been trying to convince her won't get her Ueno's attention. Here, he seems to be giving her advice to drop her act so she can perhaps deepen her friendship with the others.
Also, on page 29: is that a bottle of plain club soda? Did Ueno buy Tabata a bottle of club soda?