two questions:

1-I do stomach vaccuums 3 times a day like swanso or boss said to do...and im not quite sure what it does, i know it's part of the "core" but...yeah? what?

2-Is it good if the muscle is painful to touch the next day?

1 - they work yout transverse abdomins which is one of the muscles that support your spine
2 - hurty pain no, training soreness pain good

with all your sprinting you probably don't need them anymore

you told me that they "suck in"your stomach?

yes they also do that but it's main function it the spine and if you';ve been doing them for a while then your TA probaby works automatically so you can probably do away with them now and use a better exercise such as landmine twists, tornado ball twists etc

can you give me instructions on how to do those?

too hard to describe in writing...search google images / video and youtube too

the whole point is to "RESIST" rotation so even though your arms are moving from side to side as you'll see, your hips must stay facing perfectly straight getting rotation from the thoracic (upper / mid back) region, not the hips and lower back

check them out