From what I see, the first 4 slots are for equipment and other 8 slots are for items.
Now I want to know if there is a way to increase the amount of inventory slots, because 8 slots is really low.
There is no way to increase your inventory size beyond the 8 slots.
A character's inventory capacity is very limited as the player can store 8 items on a character (beyond what the character has equipped), plus a free private vault chest in the nexus which stores items across deaths/characters.
Players start with 1 free vault and can purchase more vault chests. Items in these chests are account-based so any items in the vault can be used to equip a new character.
Each chest can hold eight items; any items left on the floor will disappear when you leave your Vault. You get one vault to start off with, but the rest you must pay for using the money in the game.
Well, you can either buy a backpack which adds 8 more spaces, by more vaults. Backpacks are found in the nexus stores. If you can't find one go here. https://www.realmeye.com/items/misc Or you should pick up less stuff and only pick up the best stuff like pots. If you have a item you can wear, you should put it on. The best way is to make 4 extra fake accounts. 1 for items for classes that wear hides, one for items for classes that wears heavy armour, one for items for classes that wear robes, and one for rings, pots, and other stuff. You have 8 spaces in your inventory, 8 spaces in your vault, and maybe if you have luck, you can wear one of your stuff. I hope this helps.