What is the composition of the DIY-GPO?
@Webda
A maximum simple replication would consist of thesaur. ETFs in each case:
(Core:)
40% on S&P500
20% on EUROPA
20% on EM IMI
20% on WORLD SMALL CAPS

(plus invest reserve of 20% of the total portfolio value)
ETF on European government bonds
(mixed maturity with medium duration)

I have actually made it much more granular with more ETFs like Andreas Beck, and also had to make a workaround in the mix/weighting for historical reasons, as I initially only started investing with ETFs with an MSCI World alone.
(Which is not as optimal as the allocation above. But I still don't want to sell it because I don't sell/reallocate anything as a matter of principle, but only reinvest specifically in the above indices/ETFs; especially in times of crisis, but also in between via savings installments from fresh wages).

My return (since March 2020, when I started with the MSCI World):

Internal rate of return :
11.72 % (p.a.)
TTWROR (True time-weighted rate of return) :
89.18 % (i.e. on average approx. 15% p.a.)

p.s.
For my children, on the other hand, I invest in the original GPO, because the absolute costs are not so significant and it is a "fire & forget" fund of funds, where you don't have to worry about anything except making selective (or monthly) payments via an ETF savings plan.