Nicely done Alain, you may have a future as a cartoonist.
LopatNympher-
In case you are not yet familiar with all the terminology, the "sighter" is just a short (maybe 6"-18") section of brightly colored mono/backing/braided mono tied into your leader as a visual strike indicator. Try 10-14# Golden Stren, fluorescent orange/chartreuse fly line backing (20# is okay, but 30# is even better), or a short piece of brightly colored braided mono (20#). Put loops in either end of the sighter, and tie the rig as illustrated by Alain below it, and then put some heavier mono above it- for starting out in the Polish/Czech style, use about a 4' piece of 15-20# Maxima or other mono of your choice in that diameter (.015-.017"). For the long piece below your sighter/above your nymphs, make it somewhere in the 3'-6' range, depending on the size & depth of the streams you are fishing. Go shorter for brooks/small streams & shallower water, and longer for bigger streams & rivers as well as deeper water. As you get comfortable with all this, I would play around with the length of the section above your sighter, the French & Spanish often use leaders totalling 20-30', and they are DEADLY with them. For this section ( between sighter & fly line) you can use a tapered leader, or pieces of mono stepped down from say 20# to 15#, anywhere from 6' to 20', not including the sighter & tippet sections below it. Definitely start with the shorter leader though, and get used to that before you go crazy experimenting.