Rusty nails, foil & trash are just facts of life of detecting, with any detector.
Foil/tabs ring up in just about the same way a gold ring would, nothing you can really do but pick up alot of foil/tabs before you hit gold.
Do it enough, its not a question of if, but when, you score.
I've got dozens of gold/silver rings, bracelets, necklaces, trinkets in 4 [seasonal] years of detecting ,,, And have no way of knowing how much trash I picked up to find them.
That said, you can minimize trash simply by hunting a variety of areas - Some are prone to trash, some hardly have any.
At 14, maybe easier said than done, I know.
Just for kicks, you can also go in custom mode and notch out everything but, say, dimes & quarters.
Its called "cherry picking", for guys that want to maximize their chances are finding silver coins - And knowing in advance you will not likely find any nickels or gold.
That doesn't mean that every hit you get, you will now get a dime or quarter - Some objects trigger false alerts in that range also, but the 250 is often surprisingly accurate in that range.
Too, you might just fine some quarters, but they might well be clad.
As you progress, add [un-notch] halfs & pennies.
Wouldn't suggest you do this often, as you might be passing up old pennies, nickels and gold rings ,,, But its just another tool to use at certain times, may ease your frustration, and help you to get to know the machine a bit better.
If you use it enough [any machine] you will find it is telling you things you are not aware of now.
As far as rusty nails, that is another fact of life in ground digging.
The rust forms a "halo effect", and is fiendishly clever at duplicating a coin signal.
Once you dig, and that halo has been broken, the signal will often disappear, and will not signal at all, since iron is usually notched out [unless you are in all metal mode].
Again, not much to be done about it but to expect it to happen every so often, then go on and try again.
There is literally nothing you can do about it, with any machine - So since its out of your hands, don't get worked up ,,, Expect it to happen from time to time, then move on.