How to politely accept and refuse an invitation

In Nyanza during training we would have to fill out a weekly survey, rating the trainings and lectures that took place, I remember vividly being asked about our language progress if we were able to politely accept and refuse an invitation. At the time I checked yes, but now I am not too sure, I can yes to meet someone somewhere, however, I cannot say “no thank you.” Time to take out the Kinyarwanda book.
Today was an interesting day. July 4th is also Independence Day in Rwanda, so today, Monday, July 5th everything is closed. However, this was only communicated to half of the people throughout the country. When I spoke to my counterpart on Friday, the 2nd, it was clear that we were to meet on Monday, when I called him this morning to see what time he did not answer my call, no big deal, I show up at the “office” anyway. Only to find out that he is not there and others are only there because they did not know it was a holiday. It turns out “I returned on Wednesday” was heard as “I will return next Wednesday.” My mission to go to the bank and post office, well that did not happen because they were closed, there is always tomorrow. It worked out because some Peace Corps friends of mine came to town since the schools were closed, and they will have to come back again since they need to go to the bank as well. We went to the local buffet for lunch, but since the buffet was closed they were only serving chips (fries) and brochette, this sounded like a great option, until the brochettes came out and we found out that they were liver. Not exactly the part of the goat (I think goat) that I was expecting.
Just like in American it is good to leave a spear key to your house with a friend, the irony of the situation is that I gave my friend Charisa copies of all 3 of my keys since she sometimes uses my electricity during the week to charge her electronics because she doesn’t have electricity in her village and I am often out doing field work and am not around to let her in. Today we took the big step and I gave her my spare set. The ironic part is that when she got back to her village she called me looking to see if she left her key at my house because she couldn’t find it. Her neighbor was able to pry open the door and is she going to get new locks tomorrow and then going make sure someone has the spare set.
In the evening I went to my host family’s house. Here is the point of needing to know how to say “no thank you.” My host family is amazing, great people and wonderful to be around. And if I spend enough time there food usually appears. My host mother tells me to always ask the umucozis (house girls) for food if she is not home but im not comfortable asking. I have no complaints about Rwandan food either, a lot of starch-rice, bread, potatoes, but they also have vegetables and beans. The food is generally not prepared the way I would, but im not in any rush to do all my own cooking everyday, especially on a kerosene stove in a corner of my house. So today after hanging around with the kids for a few hours my host dad came come and told me they were having friends over. The friends came, we talked, I introduced myself, we drank tea, had peanuts, then I was about ready to go home. And out comes the cassava bread, I wish there was a polite way to say, “no thank you I am full”, because that just isn’t an excuse here. You can get out of anything by saying you have to wash your hair or do your laundry but when it comes to eating you have to eat it. Being ‘big’ is a sign of wealth, you can afford to eat, everyone here wants to fatten me up! Cassava bread is a similar consistency to uncooked pizza dough but grainier, they dip it in an oily sauce with a piece of fatty meat. It is not that I hate cassava bread, but it is not on the top of my list of Rwandan foods, so I dipped and ate and did the best I could, but there is a point when enough is enough. So now hours later im still full, and in no rush to have cassava bread again anytime soon. The though is nauseating, lets hope for veggies and potatoes tomorrow!