Hi Danyel, I see you are working on tense :) . A lot of the differences are related to what you are trying to emphasize. We have been playing in the park. = This is present perfect progressive, which is used to indicate duration (how long something was being done.) So we would usually say * We have been playing in the park for 2 hours now, so we're hot and sweaty. or *Question: "Where have you been all this time?" Answer: "We've been playing in the park." (The idea being that they've been in the park for a while.) & We have played in the park. = present perfect. One of the uses of present perfect is to indicate an event that happened at an unspecified time in the past. So, for example *We've played in this park, but we've never played in that one." or "We've played in the park before and it was a lot of fun." & We had played in the park. = past perfect, used to indicate that one event happened before another in the past, e.g., * We had played in the park before we went to the zoo. [park happened before zoo] & We had BEEN playing in the park. = past perfect progressive, used to emphasize how long an event was happening before another event occurred, e.g., *We had been playing in the park for just a few minutes before it started to rain. [so the two events are playing and rain starting] or *We had been playing for hours before my mom said we had to go home. [two events are playing and mom talking]