All four sentences are conditionals. Let's start with the first two.
- If you spoke English, you could get a better job.
- If you spoke English, you would get a better job.
The only difference is "would" vs "could". Would means it's likely or certain you'll get a better job. Could means it's possible.
The last two sentences use a stronger form of the past tense. Technically, they use past perfect instead of past simple.
- If you had spoken English, you could have got a better job.
- If you had spoken English, you would have got a better job.
These two sentences imply that the possibility of getting a better job is already in the past. Kind of like saying the person missed out.
Technically speaking, the first two sentences are called second degree conditional, and the last two are called third degree conditional.