em	in/on/at (position/movement)
sobre	on (top of) or over sth (position/movement)
a/para	"to" a destination (position/movement)
por	through/around (without a clear path) (position/movement)
atrás de	behind
em cima de	on top of
por cima de	on top of/moving over sth
em	in/on (days, months, years, durations)
a	for time measured in hours
atrás	ago
conversar com	to speak/talk with/to
olhar para algo	to look at/towards sth
tocar em algo	to touch sth
falar com alguém	to speak/talk with/to someone
falar de algo	to speak of/about sth
pensar sobre algo	to think about sth
falar sobre algo	to talk about sth
pensar em algo	to think of sth
falar em algo	to speak of sth