Student or Learner
According to Practical English Usage (p. 265), it is not OK to say, '
I'm going to leave now, not to be late' but OK to say, 'I'm going to leave now, so as not to be late.'
I've two questions regarding that:
1- Can we use 'not to' in spoken English?
2- Can we use 'not to' in 'not only, but also' structure as in: I've come here, not only to see you but also to tell your father that I love you.
2. The second sentence is grammatical, but you didn't use "not to".