Japanese by Example
Learning through examples in manga

Don't know with わかんない

ひとりぼっちの○○生活 » Volume 1 » Page 36

Nako learns of Bocchi’s necessity to become friends with everyone in class.

なこ:
全員(ぜんいん)友達(ともだち)かー」
"Friends with the whole class, huh?"
大丈夫(だいじょうぶ)なのかー?」
"I wonder if you'll be all right."
ぼっち:
わかんないでも頑張(がんば)る!」
"I don't know, but I'll try my best!"

わからない contracts here to わかんない.