The inventory is opened with the <Tab> or <I> key. This is a notepad with 11 pages, which can be switched using buttons in the left column. There is a certain limit on the total weight of items that a character can carry. If the limit is minimally exceeded, the character cannot jump or run, and stamina is consumed even for walking. If the limit is doubled, the character cannot walk.
On the "Weapons" page you can choose which weapon the character will use, but it is easier to use hotkeys.
On the "Clothes" page you can change items of equipment. Each item has special properties, do not forget to change clothes depending on the situation.