German citizen here. I lived several years in the US before moving back to Europe.
First: Congrats! You are doing well in general. Especially regarding your flexible self employed income side.
Regarding P2P Lending:
You are vastly underestimating the long term risk of these loans.
And with that I dont mean one loan that could default. Im mean the companies where you are "investing" through.
This are East European junk bond rated loans for people that often are not getting any money from their east european banks.
So in a real recession you will likely have something like 15-20% of those loans defaulting in a short time frame.
But thats not the real problem.
The 500 pound gorilla in the room are the East European corporations that are connecting you with the lenders.
They all have kind of limited liabillity structure. When some of them default in the next recession, most of your invested money (principal) is likely gone.
The loans may still exist but most of the lenders will not honor them.
The "compensation guarantee" that some of those entities offer for single loans, work only as long as the limited liability entity itself is existing.
So this guarantee has no real value! When you really need it, it will probably fail.
Cannot happen?
Just happened in China, where the whole P2P market collapsed:
https://www.reuters.com/article/us-china-lenders-p2p-insight/beijing-struggles-to-defuse-anger-over-chinas-p2p-lending-crisis-idUSKBN1KX077https://www.bloomberg.com/news/articles/2018-10-02/peer-to-peer-lending-crash-in-china-leads-to-suicide-and-protestBroad passive stock market ETF΄s on the other side are the safest thing there is over longer time frames.
Your principal fluctuates over the short run but is not at risk of being lost.
On top of that the real taxation of stock market ETF and single shares is much better than with P2P loans.
If you are an passive stock market investor, only the dividends are taxed which are less than 40% of the total real long term performance of the stock market .
On top of that, inflation is also not taxed with passive held stocks/ETF because like real estate, over the long term this is automatically covered with adittionally rising asset prices.
With your P2P investment your tax situation is horrible. Adittionaly to the 30% on your whole gross yield, your invested principal is loosing value due to inflation. Even if you would get 7% long term gross yield after Belgian tax with P2P which I hihghly doubt because of the points discussed above, you have to substract an adittional 2% from that for inflation of your invested principal.
I would highly recommend that you diversify into passive stock market ETF. Vanguard is also active in Europe now with their Ireland based ETFs.
The Emerging Market or Asia Pacific ex Japan region has a very attractive valuation at the moment (~3,5% dividend + ~4,5% growths from stock buybacks & growth plus covered inflation). Over the long term this is beating any P2P investment after tax & inflation with ease and on top its zero risk compared to very high risk.
All the best and enjoy your day!