Hold on a minute!
TamaSabian,
As you are in Peru, I assume English is not your first language, so if you do not understand something I say, please tell me and I will try again in a different way. This may take some time, so we will need patience with each other.
Somebody please correct me if I'm wrong, but I beleive the Delta 44 does not have mic preamps. This means you will still need either a mixer (such as you have) or a channel of preamp for every microphone that you intend to use simultaneously.
And just so you know, your SBLive really has 2 inputs, 1 left and 1 right. They are just on the same physical jack (input). What you need is called a splitter. This can be a cable with connectors at both ends, or a solid plug that looks like a 'Y'. One end needs to be a stereo mini plug, to go into the SBLive. This looks like the end of the cable to a pair of Walkman-type headphones. The other end should split into two 1/4" mono plugs that will plug into the L and R Main Out jacks on
the MX802. You may not be able to find a mini to 1/4" cable, but you can probably find a mini to RCA-type cable and then use two RCA to 1/4" adaptors. When you get the Delta44, you will need balanced 1/4" plug to balanced 1/4" plug cables to go from the 802 to the Delta. With some creative cabling, you can still give each of your 3 mics (actually you can do 4) individual inputs to the Delta, but you will lose some of the functionality of you mixer by doing it that way. The best and easiest way to do things would be to buy a new mixer that has direct outs on each input channel. I'm sure everyone would recommend a Mackie (mixer). If a Mackie is not possible (too expensive or not available, you could get by with the next step up in Behringer mixers, the 1604 (which I have, by the way). Or, you could even get another 802 or even a 602 and use it at the same time as your 802. Not pretty, but it would work.
Good luck, and feel free to ask questions!