Indeed you need to check the entry requirements for travelers from Sierra Leone into France (and quite likely Belgium and the Netherlands; it depends how far back they look at there you have been).
And of course to keep in mind that the rules in place today in late September may well have changed by December — so no matter what you learn now, you have to keep checking (to see if France etc change the categorization of Sierra Leone and thus the entry rules for people coming from there).
You can check France’s rules and categorization here (in English):
https://www.interieur.gouv.fr/Actualites/L-actu-du-Ministere/Certificate-of-international-travel
A quick review shows that for now, France categorizes Sierra Leone as Orange/amber, which is good as it means that since you are vaccinated, you can enter with proof of vaccination (and don’t have to fulfill any other requirements). However, you want to watch to make sure that Sierra Leone doesn’t drop to red.