If it were easy........
It's not, it's really hard.
I'm not frustrated, you've jumped in at the deep end, trying something totally new for you, you've put yourself out there, so respect. I've been through the learning curve so know some of the issues you are dealing with. Taking photos of people without asking; watching the subject and background in a moving frame etc. You are also having to deal with learning to read and understand a new visual format, Street Photography.
You said you've been doing research, looking at some Street Photography. Which photographers? Winnogrand, Meyerowitz, Moriama, Klein, Gilden, Cartier Bresson.........? From the photographers you've looked at, which ones did you like? Why? What kind/style of Street Photography do you like?
On another thread you asked about lenses. There was a mixed response, but the majority were saying wider rather than longer (you do have to read between the lines to see who really know what they are talking about - not many!). I asked for someone to post some examples (good examples) of long lens Street, there was one put forward, diCorcia's Heads project. A great piece of work, but really pretty unique in the world of Street (is it even really Street?). You opted to get the 135mm! 100mm longer than what is really the standard Street lens. You are going to be fighting against this, it's going to be difficult to capture something that is not a standard portrait or just photos of people in the street (not all photos in the street are Street Photography, most are just that, photos of people in the Street.) I will keep coming back to this. I think you are going to have a really tough time with this lens to capture anything that is, to my mind, Street Photography.
With regard to the nun. Usually for a side on walking photo like this, the subject is walking somewhere. A standard framing is similar to an earlier photo you posted on the other three with the man and woman crossing the street. Too much space, too close...this is the balancing act. I'm not really a fan of side or back photos, get in front of them, get the face. Of course there are lots and lots of great side and back photos though!
I guess you would have stumbled across Erik Kim's blog by now. Love him or hate him, read the blog. Loads of really helpful articles there. You use flickr, so check out the HCSP group. Read the discussions. This is a heavily curated group, a real tough bunch. Again, love it or hate it, look at the pictures, read the threads. Some Street photographers have cut their teeth through this group, Two Cute Dogs (Charlie Kirk), Dirty Harry, and Maciej Dakowicz are examples. Use Youtube to find clips of people like Winnogrand, Gilden, Meyerowitz, Mariama working. Look at the website of the In Public collective, the most important Street Photography collective.
I'll help you as much as I can. I'll help anybody if I can. I want you to be successful. I've attended a Bruce Gilden workshop in the past. I've taken the knocks. He just says it straight, and to your face..."It's cr*p", for 4 days. You just have to get up, get out again and keep trying.
