Make it so that when you equip a weapon from your inventory into your primary or secondary slot, it becomes visible on your character’s body. This would make the game more realistic and could also improve gameplay.
For example, if you store a weapon in your inventory (backpack), it should not be visible unless it is equipped in your primary or secondary slots.
Additionally, there should be a sling or strap attached to the weapon that holds it on the character’s body, similar to how it works in real life. This would make the overall appearance and movement feel more realistic.

When you equip your weapon, the sling attached to your body should disappear because the weapon is already in your hands.