If this is your first time injecting opiates please be very careful with your dosing, start at the low end to get a feel for how the drug feels this way. hopefully fentanyl isn't as common an additive to heroin where you are as it is here in the USA.
also this might be a no brainer, but i recommend boiling your shot in a spoon or whatever even if the heroin readily dissolves and you're using pre-sterilized water already, because the heroin itself is not considered sterile. you don't know what kinds of microbes have entered it from yours and your dealers' hands, let alone the spoon, etc. when you inject you are putting on the act that you are a professional performing surgery on himself to get well; it's part of the fun so do it well and you'll get through it alive for the next show