I know that when we use "det är + adj", adj will end in -t, with "den är + adj" it doesn't change and with "de är" we use -a, but i don't understand the structure with han/hon/du/jag är... do we use en form like "Han är snygg" or can we use det form like "Han är snyggt?" If anybody could answer (pleaseee) i'd appreciate it very much.
After han/hon you use the same form as after den. This is the en-word form or utrum which is the opposite of neutrum (the ett-word form), because Swedish has only neutrum and not-neutrum (utrum) - no female and male grammatical gender. In other words all female and male people are in the same grammatical category as den, so the adjectives also change in the same way.