Because calling this a bonsai is an offense. It is just a cut off stick in a pot, with pebbles that probably are intended to be decorative but should not be there.
20 years is a long time and a lot of work on something you know nothing about. There is a species guide on this site it will help with the proper care. I would plant it in the ground and let it grow it will thrive and grow more doing so. Best of luck
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