If I do kindness because I want God to give me rewards / presents , what kind of kindness is this ? . Is this kindness fake / not genuine ? Insincere kindness ?. Does God love humans who do fake / insincere kindness ?
No. Every action has an intention or motive or incentive behind it (and those who say otherwise are mistaken). So a person's intentions can either be for worldly reasons [in which case it is insincere/vain] or it can be for Allah's (ﷻ) sake (His Pleasure, His Reward, etc).
Doing kindness with the intention of seeking Allah's (ﷻ) reward is perfectly fine. There are many ahadith in which we are told that we will be rewarded if we do acts of good with the intention of seeking Allah's (ﷻ) reward (e.g., prayer/fast, spending on family, etc). Had this been blameworthy, we would then not be subsequently rewarded and would rather be rebuked. But that is not the case.
Hope this helps.