FOSS gamedev and creative worlds

Hello,
I installed the Saturn game and played it, but after I played it gravity for other games changed too. Sometimes it got disabled, sometimes swapped around.
Now I need the mod "sapier", to fix this, because it includes a gravity changer. Sadly I can't find it anywhere in the web. It includes a new ore,called sapier, similar to mese, but blue and a sapier toolset. It too includes a gravity changing tool and a blue potion.
EDIT:Too sapier coal and torches are includet.
EDIT:The gravity is only corrupt, when I on my own online worlds or in singleplayer.

See if there is something relative to " gravity " in minetest config file .

Sounds like your .conf file is setting gravity in singleplayer, look for 'movement_gravity = ???' and delete that line. Or find that in advanced settings menu and change it to 9.81.