Make many chests at your base. You can even leave chests out in the wild and mark them on your map to come back to later. Figure out what you really need and don't pick up so much heavy stuff.
It takes a while to figure out inventory. Actually it is a mini-game you will deal with for the rest of your Valheim life. Welcome to pergetory, or hell for hoarders.

And boats. Longships and Karves can hold unlimited weight, and can carry a lot. Karves can only carry 4 stacks of items, but longships carry much much more.

U just can install some mods that can give u backpacks

Yes. Not sure if you want the details spoiled though.

A not-too-spoilery thing is that you can make a cart that can carry a lot of weight for you. You unlock it once you craft and pick up bronze nails. There's also a certain item that can increase the max weight you can carry.

Other than that, you will have to use a mod.