I'm confused about pronouns: when should I use 'y' and when should I use 'en'

Y and en although pronouns, act as if they were adverbs - they are used to replace wrds in a phrase that denotes quantities, qualities, properties and relations.Firstly, the pronouns 'y' and 'en' have different meanings: 'y' means 'there' and it replaces indirect objects that end with "à" + a place and "en" + a place. For example "Je suis allée à la piscine" changes into "J'y suis allée" when you already know the subject of the sentence, in this case "piscine" so you say I went there. Another example could be: "elle va en France l'été prochain" which changes to "elle y va l'été prochain" she is going there.'en' means 'of them', 'of it' or 'some' it replaces indirect objects following "de" about quantity. It also comes before all parts of the verb. For example: "elle a bu du café" changes to "elle en a bu" if we already know what she has drunk. Or "ils ont beaucoup d'argent" which changes to "ils en ont beaucoup" they have a lot of it.