I've got a questuon
Could anyone explain the differences between back up, to assist and to support? Which contexts are more appropriate to use one and the others?

One example would be:

I have decided to back you up.
I have decided to support you.
I have decided to assist you.

Thanks in advance.

Question

I've got a questuon
Could anyone explain the differences between back up, to assist and to support? Which contexts are more appropriate to use one and the others?

One example would be:

I have decided to back you up.
I have decided to support you.
I have decided to assist you.

Thanks in advance.

Answer

Back you up = verbally agree/say that yes, you are correct/say that you are not lying

Assist = physically and tangibly help, e.g. write part of the report, do some research for you, contact places...

Support = more general meaning; perhaps you assist, perhaps you provide emotional support/listen to their problems, perhaps financial support, perhaps business advice, perhaps you back them up, etc.