There are plenty of merchants in the game with many different things for sale, you have to be more specific. Any specific item you're looking to buy?

I wish game didnt have so clunky movement, im looking forward remake

There is one NPC who shows up partway through who you can more or less sell things to, though in general most items that drop from random enemies are only worth 50 or 100 souls, which is basically nothing once you get to higher levels.

Items you don't have equipped don't weigh anything, but if the cluttered inventory bothers you, you can buy the Bottomless Box from the merchant in the Undead Burg for 1000 souls. You can access this from any bonfire and it allows you to store things until the NPC I mentioned turns up.

It's the same for every Fromsoft game, but I'd say to avoid online multiplayer in some of the earlier areas. The amount of tryhard twinks you'll meet is ridiculous. It becomes much more bearable and actually fun when you're playing on an even playing ground sometime after the gargoyles.