رَبَّنَا آتِنَا فِي الدُّنْيَا حَسَنَةً وَفِي الْآخِرَةِ حَسَنَةً وَقِنَا عَذَابَ النَّارِ
Rabbana atina fid-dunya hasanatan wa fil-akhirati hasanatan wa qina 'adhaaban-nar
Unser Herr, gib uns Gutes in dieser Welt und Gutes im Jenseits und bewahre uns vor der Strafe des Feuers.
Comprehensive dua that can be said before salam or anytime
This was the most frequent dua of the Prophet (PBUH), asking for good in both worlds.