Gonna, Wanna, Gotta
In spoken English, native speakers tend to slur their words. It is extremely common and sounds natural to do so. However, these words are rarely written and should be avoided in formal situations.
I wanna get high- Quiero colocarme
He's gonna freak out when he sees you- Él va a flipar cuando te vea
You gotta work your arse off if you wanna make it in this life- Tienes que currar como un burro si quieres triunfar en esta vida
The word because is often shortened to 'cause or cos in spoken English, but it should be avoided in writing.