"Mais ce n'est pas le joyeux ..." means "but is is not the merry ..."
It means "But French is very difficult"
'mais quelle est cette ...' means but what is this (thing) / who is this (person).
This isn't a complete sentence, but what you wrote translates to "...'who' but it's okay".
"Life is joy" in French is "la vie est joie."
The cast of Fouinard est joyeux - 1911 includes: Georges Vinter as Fouinard
Oui, mais mon français est pauvre ces jours-ci
''Is absent but hates him''
Mon français est un peu rouillé mais j'essaie
la vie est très stressante mais je l'aime quand même
"Mais si je mange", means "But of course, I eat." Naturally, the question would be "Do you eat?" which is "Est-ce que tu manges?" in French.
elle est très spéciale mais cool
Elle est drôle, mais un peu paresseuse.