Dendrobium - how to look after it - what to do with it?

[19ninety]

Hello,

I have what i believe is a Dendrobium. I dont know which type it is (excuse the terms, I'm new to orchids) and it seems to be growing a lot.
I was given this plant by my girlfriend who saved it from her shop where it was going to be thrown out. I looked as if it has recently flowered when I first got it as its has the remains of petals all up the main stem (which can still be seen).
I didnt really know what to do with it so stuck it on a bright window and kept watering it every week or two with a little feed (weak baby bio) and it seems happy enough. At one point the main stem shriveled a little and I thought it was dieing ... then this week its plumped right out again and the whole plant is looking a lovely strong green.
Now since getting it it has grown a fair bit and is looking a little untidy and I'm wondering what I should be doing with it now?? I dont want to just leave it if doing so will cause it to get all scraggely, over grown or thinned out.
I've attached some images below.
Any help of advice is greatly welcome

Thanks

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