Spending two days in a lab can easily save you up to one hour reading literature
Following: a few pre-formulated responses to common, questionable design decisions and typical problems.
This is a canned comment to let you know that it looks like you're trying to implement something that is non-trivial with the power-hungry NE555 but is very easy for someone using a microcontroller.
This is just a canned comment to let you know that what you're trying to build from discrete analog components (possibly incorporating Opamps and/or NE555) is a digital control problem and thus can easily and with lower parts count be solved with a microcontroller with really minimal firmware to write.
I'm voting to close this question as off-topic because OP has bought a device from a supplier that doesn't supply a datasheet. Device doesn't work as expected for application. Since no guarantees made by a datasheet can be expected, there's nothing to answer here: Get a device that comes with a datasheet that guarantees operation under the conditions that you need.
I’m voting to close this question because this homework question without any attempt gives no indication where the asker is actually stuck, and hence no indication what they actually need help with. As such, the question is inanswerable (short of giving them a grounds-up education from high-school level math), and should be closed.