PRESENT PERFECT is used to express an event that happened in the past that has present consequences. The PAST PERFECT tense is used to show that something happened before another action in the past

Buenas tardes Isaac, espero que esto te quite las dudas y sepas en que condiciones usarlos Could, indica posibilidad o habilidad en el pasado. por ejemplo : 1.- Isaac could speak English when he was young. 2.- I couldn’t sleep last night. Tambien lo podemos usar para posibiliad en el futuro por ejemplo: 1.- You could pass the exam if you studied. 2.- I think it could rain later. “could” puede solicitar permiso o preguntar sobre las posibilidades, pero es más formal. por ejemplo: 1.- Could you help me? 2.- Could you pass the sugar please? May para indicar posibilidades en el futuro. por ejemplo: 1.- It may be better to finish this now, rather than wait until tomorrow. 2.- I would bring an umbrella, it may rain later. También se puede utilizar para dar permisos o instrucciones. por ejemplo: 1.- You may leave if you like. 2.- You may use your cell phones now. En frases interrogativas, el uso de “may” por ejemplo: 1.- May I have a glass of water? 2.- May I leave now? Se usa “might” para indicar posibilidades en el presente o el futuro. Por ejemplo: 1.- I would bring an umbrella, it might rain later. 2.- It might be better to finish this now, rather than wait until tomorrow.

PRESENT PERFECT is used to express an event that happened in the past that has present consequences. The PAST PERFECT tense is used to show that something happened before another action in the past