How to save/invest best

Good day, regarding the initial situation we are both 24 and have a son who is 2 months old. Currently, my wife is on parental leave where she receives about €850 with child benefit, my income is about €2200. We want to build a house in about 6-7 years. After all deductions, we can save about €700-800 per month. How should we invest the money most advantageously, building savings contract etc. Thank you very much in advance. Regards David

Can't edit the post so new post sorry

We had the following idea: 2 home savings contracts with Riester
1) 75,000 <--- monthly 350€
2) 25,000 <--- monthly 100€

the rest approx. 300€ goes monthly into a daily allowance account in case something comes up, bigger repair etc.

All 3 things run for 7 years

My brother-in-law built solidly 115 sqm about 100,000 € the house.
The plot costs about 55,000 here.
Additional costs I leave open approx. 20,000-30,000 as I have read here in the [Forum].

I would need about 180-200 thousand, if anything is missing please say =)

I would appreciate a few tips, thanks.