You can double-spend
Whilst it is *possible* it is actually in practice rather difficult to do (I tried once after making a huge mistake with fees doing a raw tx).
Any node that has seen the first tx will ignore the "double spend" attempt - making it virtually impossible to then do so after only a few seconds across much of the network.
Indeed, you can't do this immediately but the saying "you can't double spent" leads newbies to fear/feeling scammed/posting aggressively in the tech forum.
So:
Yes we can.
But you'll have to use the search function to find the guide and to wait a bit.