Safest way to store BTC

Hello.

I've got BTC as my retirement plan (per the following steps):

1. Save up to 40k euro
2. Buy BTC
3. HODL
4. Buy government stock in 2 years
5. Life of, of half the dividends as the capital culminates.

My question is how can I store 400.000-500.000k worth of BTC?

Please don't reply if you can't be decent and respectful.

Thanks in advance!