Question

change into positive and comparative:Hari is not so tall as varun​

Answer 1

Varun is tall ( Positive )
Varun is taller than Hari ( Comparative )

Hope that helps.
But I want to make one thing clear that whenever we talk about two people , a comparison is being made. So it cannot be converted into positive degree ! That’s why I’ve talked only about Varun

Answer 2

ᴀɴsᴡᴇʀ-:

$\blue\implies$ᴘᴏsɪᴛɪᴠᴇ-:

$\sf\pink\rightarrow$Hari is as tall as varun.

$\blue\implies$ᴄᴏᴍᴘᴀʀɪᴛɪᴠᴇ-:

$\sf\pink\rightarrow$Hari is taller than Varun.

ʜᴏᴘᴇ ᴛʜɪs ʜᴇʟᴘs:)