You should invest in the Tomorrow Better Future Stock fund for the long term, i.e. not depend on your invested money for at least 7 years. If necessary, you can of course still sell your shares at any time according to the applicable trading conditions via the Tomorrow App. 

Always keep in mind that even though the risk in a stock fund is spread, this does not guarantee that your invested money will not lose value in the recommended time. Investments are never risk-free.