Irms - In my case I had a lumpectomy and sentinel node biopsy (on my dominant arm side) as day surgery.
The next day my arm movement was limited but with care I was able to use a keyboard and mouse and do basic things. I used my non-dominant arm for a lot of tasks such as putting away dishes, brushing teeth, etc. I was a bit tired.
By day 4 I was driving a bit but getting out and about made me tired.
By day 8 I went back to work. I have a physical partly-outdoors job so I had to make sure to get my colleague to do any heavy lifting, and I took moments to sit inside and recover after walking around too much. A few times my legs felt a bit wobbly. It was hard and tiring but it felt good to be moving and doing normal things.
There were a lot of weird sensations that happened in my armpit and arm so at times I had to grin and ignore it while face-to-face with customers.
As for radiotherapy, the Optimal Care Pathway says that radiation therapy should begin within 8 weeks of surgery for patients who do not have adjuvant chemotherapy.
In my case, two months after the first surgery I had a second surgery to remove more lymph nodes - the surgery would have been sooner but my surgeon had holidays booked. The recovery from that was more intense and I was off work for two weeks.
6 weeks after the second surgery I began radiotherapy - that might have been a bit sooner too except we'd hit the Christmas/New Year's period.