Just be patient and ride on easy roads with no traffics for now...
What you are experiencing is normal in motorcycles, and there are two tricks to help you with that issue.
See, gears on a motorcycle go crazy, and if you rush it, it wont shift, so if you wait until you get to almost a stop and then you start to hit the shifter trying to bring it down to first quick, guess what, it won't do it...
When riding a motorcycle, you can not be lazy, you have to stay on top of the game at all times... That means that you have to be thinking ahead when coming to stop and start shifting down one gear at the time as you come down in speed. Down wait until you doing 5mph and then try to shift down all the way from 5th to 1st in a second, it won't work. If you know you are going to stop or slow down to about 5mph, then learn your shifting speeds and do your shifting ahead of time while the process is happening...
Now, if you did forgot to do it like it happens to all us, you got distracted, before you know you are a full stop with the bike in 5th gear, you hit the shifter and the bike doesn't want to shift... Here is the trick...
At that point, let go of the clutch slowly until you feel the bike engaging... Wanting to pull out... At that point, hold the cluth where it is and start shifting down and you will see that the transmission will react... It is a mid point in the clutch travel where its not enough to get the bike running, but it is just enough to get the gears engaged. You do not want to find yourself doing this at a red light when there is a car coming behind you... Not a good idea...
The best option is to use engine breaking, which means that you shift down as you are coming down on speed, this will guarantee that you will always be at the correct gear at all times, weather you are coming to stop or slowing down to take a corner...
Remember stay on top of the game at all times by using engine breaking...