I am an English teacher so I can take a stab at the tenses thing - English doesn't actually have a future tense. We either use the present continuous (I am eating) combined with a time word or phrase (I'm eating at John's tomorrow) - this is when we're talking about plans rather than anything actually concrete. It feels transient, because using the present continuous in the present is very transient. I'm eating (now, but I won't be in five minutes). It's not the tense we use for permanent things such as "I don't eat meat". In fact although it's correct to use present continuous for current states which will at some point come to an end, there are several words that we never use in present continuous such as "love". We don't say "I'm loving him", we say "I love him". If we consider a house move to be temporary, we say "I'm living in London at the moment" but if a place feels like home, we say "I live in London".
The second way we express the future is to tack "going to" in front of whatever it is. "I'm going to visit my grandparents next week". This is more concrete but because it uses the word going it also has this sense of a journey, of time passing.
Then the last way that we express the future is to use the word "will" in some sense, whether it's alone (I will be there) or in conjunction with an adverb expressing the probability. (It will probably rain, I'll definitely get one of those, it's unlikely he'll make it.)
In fact we hardly ever use "I will..." alone. We use it typically when making spur of the moment decisions "I'll help you!" or to emphasise if somebody implies that you won't/can't do something, you might reply with "I will do it!"
If you look into the etymology of the word will, it does mean to choose/make a decision, but there's also a much stronger bias towards the meaning of wishing, desiring, hoping. It's similar to the verb use, "willing something to be true". (While checking I was right on this I also came across "shall" which of course can be used in place of "will" to express a future course of action, but it's old fashioned these days and rarely used. The meaning of shall is more couched in obligation.)
Then there's the if/when distinction. We use if for situations where we don't know the outcome and when for situations where we expect something to happen. Other languages don't necessarily have this and tend to use when for both. So it seems that we hedge our bets quite a lot with the word "if" (it's one I was told specifically never to use when addressing students with a low or intermediate level of English, because they often find it confusing).