Hi there,
The word 'whether' has to be followed by one of 2 things:
- A full sentence with a subject and a verb: 'Nowadays it is difficult to decide whether YOU (subject) SHOULD AIM FOR(verb) a high salary or an enjoyable job'
- an infinitive: 'Nowadays it is difficult to decide whether TO AIM FOR(infinitive) a high salary or an enjoyable job'
This means that the phrase you have above doesn't work in English. So instead of 'whether', I would say that the best alternative would be 'between':
'Nowadays it is difficult to decide BETWEEN a high salary or an enjoyable job'
Hope this helps!