How to convert special characters in PLSQL

I have to import data on table and through an interface and these datas come out with a different spelling as what I was intended to. For example, I got père instead of père, Président instead of Président and l’Aiguille instead of l'Aiguille.

I tried the solution found here Fix corrupted characters (e.g. umlauts) in a string using ORACLE SQL and convert it to proper UTF-8 but it doesn't seem to work with some characters.

For example, select convert('Président','WE8MSWIN1252', 'AL32UTF8') from dual works and returns Président.Though, select convert('père','WE8MSWIN1252', 'AL32UTF8') from dual returns pÿre instead of père and select convert('l’Aiguille','WE8MSWIN1252', 'AL32UTF8') from dual returns l¿™Aiguille instead of l'Aiguille

EDIT : When I execute the query SELECT VALUE FROM NLS_DATABASE_PARAMETERS WHERE PARAMETER = 'NLS_CHARACTERSET';I get WE8ISO8859P15 .When I execute the query SELECT VALUE FROM NLS_DATABASE_PARAMETERS WHERE PARAMETER = 'NLS_NCHAR_CHARACTERSET'; I get AL16UTF16

Do you have a way to convert properly these characters please?Thank you in advance.