how do you raise funds when you don't have enough money to add liquidity?
This is like asking how can I invest when I do not have money to me. Go get some work and earn money.
why do we have to deposit to add liquidity?
When you say
add liquidity, that literally means contributing to a money pool. You should read this article before you ask further questions -
What Are Liquidity Pools in DeFi and How Do They Work?^ If that's too complicated for you, type
liquidity pool explained on youtube. There should be plenty of short videos you can find there.
Any other platforms to raise funds without adding funds?
Charity