Hello guys, because cryptos are dropping now it's a good time to buy but i have one worry i have to ask about.

This guide says that we should not make transactions (send/receive) before 12 hours UASF/BIP goes in on 1st of August but i have read somewhere else that there's a possibility of bitcoins from non-segwit blocks being erased after UASF goes in and gets most of mining power. Does that mean i could possibly receive a transaction of bitcoin from non-segwit blocks and once UASF goes through those btc would just simply disappear?

If that is true, how do i protect myself and know WHEN exactly i am supposed to stop making transactions? I know the guide says 12 hours beforehand but i'm reading somewhere else that signaling of segwit started earlier than 1st of August, would that mean there's already risk in buying?

It's a great time to purchase because of all the drama, bubble popping but i want to be sure the bitcoins i buy are not gonna just simply disappear soon after.