full inventory

Hi,
I've been playing SSO for some days and now my item inventory is full. Further, only the first tab with 50 slots is working; the second (and the third) tab are always empty.

Is there a way to keep more items, like a bank or anything similar?
For how many days the vendors take in shop the items I sell them? It could be a strategy to keep the items in excess?
How can I stack multiple items that are the same? For example, when I craft potions, they finish in my inventory in a different slot even if they are the same of other potions I already have.

Thanks in advance for your reply.
My in-game name is BlackSag.

there is a bank. Search for a npc with a chest symbol , it's a little boy.

Thank you very much.
I didn't noticed it was the "warehouse".

BlackSagitter wrote: the second (and the third) tab are always empty.

I think the other tabs are temporary inventory.

BlackSagitter wrote:How can I stack multiple items that are the same? For example, when I craft potions, they finish in my inventory in a different slot even if they are the same of other potions I already have.

You can either manually drag and drop the same potions onto their corresponding pile, or click the button circled below (it will automatically sort out your inventory for you.)

Spoiler: