Your hidden mmr is lower than your actual rank. In other words, the game believes your current skill level is below where you are currently playing. This actually makes perfect sense as it forces you to win more than you lose in order to climb.

Why do I lose so much LP league?

You must have a negative win rate. Your MMR would be lower than your actual division and your lp gain and loss is trying to naturally place you in the correct one. If you start winning more games, the margin between your lp loss/wins will get smaller.

Can you gain LP even if you lose?

LP Gain and loss is decided entirely around your mmr. If your mmr is lower than the average mmr of the division, you lose more lpthan you gain. The best way to change it is to just play better.

What is a normal amount of Lp gain?

This puts Solarbacca relatively even for their wins and losses; meanwhile, the average player gains something around 14 LP and loses around 25 LP (low Elo players).