will be word when we use in sentence I got confused

it looks like a very old building and the building look like very old which is between true or false sentence

घटना भूतकाळात घडली आहे मग did कसा काय आला

Which sentence for using do and did word ?

I had fever,why we are not write i was fever

hi what are you doing

hello how are you

i am confused

why use would

when we use could would will