Will learning French affect my English?
The French language is a Romance language of the Indo-European family. It descended from the Vulgar Latin of the Roman Empire, as did all Romance languages. French evolved from Gallo-Romance, the Latin spoken in Gaul, and more specifically in Northern Gaul. Its closest relatives are the other languages d’oïl—languages historically spoken in northern France and in southern Belgium, which French (Francien) largely supplanted. French was also influenced by native Celtic languages of Northern Roman Gaul like Gallia Belgica and by the Frankish language of the post-Roman Frankish invaders. Today, owing to France’s past overseas expansion, there are numerous French-based creole languages, most notably Haitian Creole. A French-speaking person or nation may be referred to as Francophone in both English and French.
The answer to your question is: No, Not at all! Go for it! You are enriching your life and language skills and I think you will find that each language will ‘support’ the other. Also, your Spanish will be a great help in learning and understanding French grammar and structure and your English will support it as well because Norman French had a huge influence on English after 1066. Something like 30% of English words has a French root I believe. Pronunciation in French is the biggest challenge along with the intonation of it but these are refinements you can always work on. In fact, languages can be mutually supportive, which is how it should be.