"I have worked with 50 people." This generally means "at some point in the past, I have worked with as many as 50 people," just stating the fact that you have worked with 50 - it implies nothing about whether that action continues or not, but generally, most would assume that it does not continue.
"I worked with 50 people." Also conveys the meaning of working with 50 people in the past - but would generally be used in a finite incident, such as, "I worked with 50 people on that project," or "I worked with 50 people at my last job." It implies that the situation does not currently continue.
"I have been working with 50 people." This sentence does imply that you are working with 50 people, and that it continues now.
"We worked with more than 50 clients." This is again a finite incident, which would be assumed to have ended. If you wish to say that you are working with them still, you need to say something like "We have been working with 50 people."
I hope this helps, and if you have other questions, don't hesistate to ask here, or post a new topic!
Many thanks for lucid explanations. It was helpful.
I dont want to be too demanding, but I cant keep my curiocity further to your explaination! (I really want to lean good english)
Let's assume the following situation -
at time T0: I was working with AA, BB, CC, DD, EE, FF, GG
at time T1 (present) : I am working with AA, BB, CC, HH, II.
Thus in-all I work with 9 different peoples over the duration of time. How I can express that. You see what I mean? My logic is crushing because at T1: I am not working with EE, FF and GG but still working with AA, BB and CC.
Here can I say "I have been working with 9 different people"
I think I know what you mean. In that case, you could say something like this:
"I have worked with 9 people, at one time or another. Many have moved on to other things, but I still work with some of them." or, "I worked with 9 people, but never at the same time, five still remain - some old, some new." And there are lots of other possible ways, too. Do these make sense to you?