Is this normal and am I safe agreeing to this? Would it be reasonable to send back a request for ammendment?
That type of clauses is not unusual, but your decision should be made only in accordance to what is acceptable to you.
Ron Beyer's suggestion of reciprocity is a valid, reasonable approach. I, by contrast, would reject any clause that involves ...
The wording in question has nothing to do with copyright. Presumably you have some other agreement that makes your programming effort a work for hire of the company or otherwise assigns them copyright. The NDA says you will keep some set of thing confidential.
What does this statement really mean? I have seen the same wording in several NDAs.
The question of waiving the copyright of source code depends on the extent, if any, to which the code entails or reflects trademarks & confidential information the counterparty needs or needed to provide for implementation of its business rules (and finding that language ...
Is this legal?
Can they enforce me to keep the NDA forever?
No, it ends when you die. Practically, of course, any confidential information you have becomes less useful over time either because it becomes non-confidential or it just goes out of date.
They also said that "The contractor take on no liability for the correctness, reliability and ...