Welcome to the group. Sorry to hear about your diagnosis. My own experience was somewhat similar to yours: hemiglossectomy (1/3) & neck dissection. Though I am surprised that you were allowed to eat so soon after surgery. I had to wait until my tongue healed, which took about a month. I was on a nasal feeding tube for nutrition during that time and my weight dropped from 195 to 172.

Fatigue is normal, and it will continue throughout your radiation and chemo (not sure if that applies to you as you did not mention). I underwent 33 radiation and 2 rounds of chemo, which was rough. You can expect bad mouth sores, which should heal up withen a month or two once treatment is done. The best thing you can do is to stay hydrated and consume plenty of calories each day. Protein will help your body heal and you should strive to get upwards of a 100 grams or more each day.

To help with the lymphedema in your neck it would be a good idea to do daily massages. Here is a link to a YouTube vid demonstrating how to do it.

Try not to beat yourself up over how you got cancer. Though you should make every effort to quit smoking if you have not already done so. Keep a positive attitude and be determined to beat cancer. You can do this.