Samatha while studying I heard about the practice of concentration. But I work 13 hours per day doing coding. How can I meditate while studying, thinking really deep?

I can focus on one static object, but not reading (coding) documentation, write code remaining in one state of completely self center
Higher levels of concentration is not possible while the mind is active but you can have some level of non-exclusive focus on like the breath or bodily sensations while working. You need to develop initial and sustained focus on a chosen object.