What I tend to do when making cordials is to 3/4 fill my largest saucepan, which is 2.5l capacity, with fruit and add enough water to just come up to the top of the fruit. Obviously if you have a larger pan, you'll be able to add more fruit than I can but, whatever the capacity, don't fill more than 3/4 full. I don't weigh the fruit beforehand as it's the end quantity of liquid that determines how much sugar I need to add, not the initial weight of the fruit.
I bring the pan to a boil then turn right down and simmer for as long as it takes for the fruit to disintegrate. Some fruit is quicker than others, and fruits like blackberry or raspberry benefit from a bit of help from a potato masher. Forty-five minutes is usually enough for even the most stubborn of fruits!
Once cooked, I strain the whole mixture through a jelly bag so all the "bits" stay in the bag, and what's left is a nice clear liquid in the bowl. If you haven't got a purpose-made jelly bag, make one out of a large square of muslin (pre-boil it first to sterilise). Drape the cloth over your bowl (I use my large mixing bowl), dump the contents of the pan into the muslin, then gather up all four corners and tie the "bag" with string. You can then tie the other end of the string to a handle on an upper cupboard (keeping your bowl underneath!) and let the liquid to drip through. Allow a minimum of 2 hours, although overnight is better.
I measure the amount of liquid I've collected, and as a general rule of thumb, measure out 400g of sugar to each 1000ml of liquid. Heat the liquid in the pan until it's almost reached boiling point, turn down the heat, then slowly add the sugar and stir until it's all dissolved. At this point a taste is compulsory :) If the juice is to your taste, you don't need to add any more sugar. If it isn't sweet enough, add more sugar in 50g increments until it's more to your liking. Provided all the sugar is dissolved and the mixture sweet enough, it's ready to bottle. Use pretty much as you would commercial "beena" and serve diluted to taste.
You'll need to pre-do the bottles and sterilise them before filling. Do this by giving them a thorough wash, then drying them in an oven set at 100C for at least 10 minutes. I leave mine in the oven until I'm ready to bottle.
And that's how I beena!