There is no figure which answers your question because of inflation and, if that does not take your savings, our banking and financial advisors will.

To survive you need two things; youth and a steady income.
The income gives you access to other people's money and helps share the risk.
You will lose your youth, but you can prepare today to ensure a steady income when you retire but be careful, only Singapore has CPF and guarantees workers retirement; elsewhere you are more likely to be dispossessed during your working lifetime.
So, any pension scheme should be private.
I agree with other posters, go to Australia (or NZ).

I think Australia has a good future and the economy can only get stronger.
It comprises a continent full of valuable minerals increasingly in demand and a lifestyle second to none.
The taxes are high, but you said you wanted to invest in the future and there is no better way of helping than to pay taxes and help build a strong infrastructure especially a professional free healthcare system.
I am sure Australia would be overwhelmed by older Expats if their immigration criteria were not so strict, so don't leave it too late, the sooner the better.
However, don't give up your European passport.

We have many problems in Europe and a spendthrift, mischievous and faceless unelected EU bureaucracy which is pushing EU-national governments far to the right of centre; and the same idealistic policies, increasingly out-of-touch with reality could one day open Australia's borders resulting in the same irreversible chaos.