I got your PM. I saw your post and did not reply to it because I don't really know the answers and I suspect there are people here who have a better idea than I do, sorry.
Remember this is an international forum, the person who can help you might be on the other side of the planet fast asleep in bed. You should wait at least 24 hours for a response.
You need to study how to charge lithium batteries - it’s not just a case of putting a voltage onto them .
The panel may or may not do the job , it needs to be sized to provide enough power for your project , not just enough voltage.
So you need to work out the consumption of your circuit over 24hr s and size a panel to be able to provide that, plus some for charging, at the various times of the year/weather conditions . Your battery needs to be sized to provide enough power for nighttime or when the sun is not out .
It is worth also looking at power saving techniques , like switching off sensors and putting the Arduino to sleep, also the regulator on the standard board wastes a lot of power , so you need to
Look at removing it , powering via the 5v pin .
I’d suggest you tackle each aspect of the project in turn , work out how to reduce the power of your project , measure its power consumption and go from there . Using a lead acid battery , which is easier to charge , may simplify things .
