How to use .so files

I recently downloaded a SDK (written in C) from a device distributor and try to compile the code. As I do so, the output is

/usr/bin/ld: FILE: undefined reference to 'FUNCTION'

I assume that some linking might fail because there are some .so-files in the SDK which need to be installed.

Does anyone how to fix this problem? I Use Ubuntu 20.04.2. I'm grateful to all kinds of help.

Regards s0n1c

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