For some folks Kaga is a great starter ship in Tier 8 because she has so many planes. For other folks, her long attack lines required on her Torps and Rockets mean that people just don't find the ability to strike meaningfully. Personally, I'm not a Kaga player as I crave more maneuverable planes.
As for losing 50 out of 58 battles, that's not a statistically significant number... but it isn't INsignificant either. That's likely a serious indication that something isn't working out well at all.
Basic concept in terms of "Win Rate" is:
20% of matches are Wins regardless of what you do
20% of matches are Losses regardless of what you do
60% of matches are Impacted by Your Influence
It's likely that you're not finding the ways to influence with Kaga, and you're also low-rolling on how the teams settle out. As someone else pointed out, the only person in every single match you play... is you. The best way to advance is to study your play and see where you can improve it.
I might recommend posting some Replays as there are several folks here that can review them and give pointers to help out.