Welcome to TP!
I think there is a lot of sense to buying second-hand. Someone else takes the big loss on depreciation (much of it as they walk out of the store). There are several reputable sellers of second-hand equipment: MPB gets used quite a bit by forum members (with occasional issues, but probably far more successes). I think there is a whole section devoted to them for a bit of background reading.
You may even find there is a physical shop near to you, because there really is no substitute for trying before you buy.
On that thought, do you have a (good) friend who might let you borrow a DSLR (Digital Single Lens Reflex) for a little go. Some models are bigger than others. Some lenses are bigger than others. You may find that you are comfortable lugging something big around (I seem to be in that camp), or you may really want something smaller and lighter. This is a really important thing for you to decide - and it's better done before you spend money.
You say that someone has recommended a Canon 800D. I'm sure that is a very good camera, but I don't know that camera myself. There are so many options available, even just within the Canon range. The chance of that being your perfect model without quite a lot of research, handling, experimenting, is slim - perhaps think why that person might have recommended it? Do they have that model and find it good - that's fine, but do they take your type of photos? Or perhaps they have one for sale? Not so fine!
Most people (me included) spend quite a bit of time, and money, trying to figure out what is best for them. Some (me included) are never sure that they have got there!
The general rule (not always 100% followed) is that Canon models with longer model names, and higher numbered, are smaller, more "plasticky" and less well featured. Of course, until you know what you need, something smaller, lighter and simpler might be perfect.
I sort of meandered: Canon 500D (very good, still use it from time to time), 5D (now sold, original model is rather long in the tooth, later versions are excellent I am told), 1Ds mk II (now put out to pasture; excellent, but very, very big - that might not suit you), 1Ds mk III (my main camera, just excellent, but big), 7D mk II (another excellent camera, with more bells and whistles than the two 1 series cameras). Probably none of these would be right for you, but I don't know, that's for you to figure out.
There are also mirrorless cameras (more choice!) which tend to be a bit smaller and lighter than their DSLR brothers.
It's all very tricky! Good luck!