We haven't had much rain in the UK and it's been warmer than average in the last three months, so I'm not surprised your soil is difficult to dig without soaking it first.
Compost, absolutely, as much of it as you can afford, but not multi purpose compost - that is intended for use in pots as a growing medium. You need soil conditioning compost, so things like composted animal manures, and if available where you are, spent mushroom compost is very useful. You don't actually have to dig it in, it can be applied as a thick mulch, but if you're digging it anyway to remove weeds and plant, fine, spread it all over and dig it in. Applying soil conditioning manure twice a year will mean the soil will improve over 2-5 years, and then its easier to use a hoe to remove small weeds.
As for weeds, they are always with us and weeding is an ongoing job, but it depends what the weeds are; some weeds are annuals and pop up on their own all the time, these are easy to remove when they're small if you keep on top of it ongoing. Other weeds are more pernicious and become permanent residents, and if they've been present for a while, can be difficult to dig out, so things like docks, alkanet (Pentaglottis smpervirens), brambles, Carex pendula and so on. Dandelions have a long taproot, but can be dug out. If you have any pernicious weeds, using weedkiller might be necessary, but which weedkiller and how effective it is does depend on which weed - brambles, which are woody based, won't be killed by something like glyphosate, and need a different approach.
Some advice on watering, both before and after planting, if you are planting permanent things like small shrubs and herbaceous perennials; if you water, do it with a sprinkler on the end of a hose, and let the sprinkler run on an area for at least 30 minutes to an hour every six days or so in dry, warm spells, rather than watering more often walking round with the hose. You don't need an expensive, fancy sprinkler, something like this https://www.amazon.co.uk/Gardena-01951-20-Classic-Spray-Sprinkler/dp/B0001E3TA8 will do the job perfectly well. When you first plant, you want to encourage the plants to put their roots down into the soil, and watering less and more often means the water will only be in the top inch of soil, and won't go much further down, so the plants will keep their roots near the surface, waiting for the next lot of water you come along and give them. It would also be wise to soak the area well prior to planting, if you have had no significant rainfall beforehand. If you're only going to plant things for summer like summer bedding, then walking round frequently with the hose is okay.