18 y/o inherited €10k, what would be best: invest for 10–12 yrs or just for retirement?

Posting for a friend: she’s 18, living in Germany, still in Gymnasium and likely a student soon. She inherited €10,000, no debt, emergency cash is handled separately. She wants to invest this money and is unsure about the time horizon.

The bank suggested investing via funds/ETFs and mentioned diversification. They specifically brought up two Deka equity funds (one dividend/global, one Europe) and an MSCI World ETF as examples, and said the final recommendation depends on a risk-profile/suitability meeting

What would you do in this situation: invest for cca 10–12 years vs treat it as retirement money? Would you keep it simple with one broad global ETF (or World+EM), and would you invest lump sum or spread it over a few months? Any Germany-specific basics to set up (broker fees/Sparplan, Freistellungsauftrag/taxes) are welcome.