DONT DESPAIR!!
I've lived with ground elder for 11 years and have developed a number of approaches. I have bought glyphosate and fully intended to use it but just never... quite..... did!
In veg beds it might be a good idea to kill it (mine dont have it thank the Lord!) especially if you're not growing for a year. Another option might be to cover/exclude light for two years but this sounds a bit extreme. Perhaps someone else will have ideas. I know the areas I cultivate regularly it never gets a hold.
On the lawn it sounds as though this has been allowed to grow long. Where we mow regularly all the ground elder has disappeared. Perhaps it would return if we stopped mowing. I suggest you just mow rather than using the bottle. Keep it quite short for the first couple of years but we now let some areas grow spring wildflowers and the elder has not returned in five years.
In borders I have mostly tried to dig it out in small manageable areas. each area is then planted with Geranium machorrizum which appears to really inhibit the elder. Any elder leaves that appear get the three 'R's - Ruthlessly Regularly Removed! I then gradually introduce the plants I want by removing chunks of the geranium as and when.
In wilder areas I've had some sucess with using a 1m circle of landscape fabric and planting shrubs through them - partic good are species roses (dont try the wussy kind), viburnums and amelanchier. Or just appreciate the plant! Ground elder is actually quite pretty - good ground cover (!), scented, umbelliferous flowers that attract hoards of hoverflies and the birds like the seeds. I let it do its thing in selected areas.
I also have one small patch that I actually feed! It produces long succulent shoots in late March/early April that taste like spinach long before I have much fresh greens in the veg garden. Cook it longer than spinach and be really generous with the butter!
Sorry if this is a bit long but I remember how daunting it was at first and really hope that some of the above gives you hope!!