I adjusted my chain, correctly, but some times when I check it, it feels to tight. If I roll the bike forward a bit it goes back to being correct looseness, is the normal?
@marc covers the adjustment process well.
However, uneven tension is a sign of wear, and can be a cause for chain replacement.
Every chain driven bike has a maximum chain slack, and a minimum.
Chain slack should be adjusted to the minimum allowable slack at the tightest point.
After adjusting, the loosest point must also be checked. If the chain slack is above the maximum allowable at the slackest point, then the chain is worn out, and must be replaced due to uneven wear.
Usually, if the chain has worn out, the sprockets should be replaced as well. This is because a worn sprocket can greatly accelerate wear on the chain.
It is common for a chain to be tighter in certain spots than others, owing to some slight eccentricity of the sprockets.
The generally accepted practice is to adjust chain tension relative to the tightest spot you can find, so that you avoid creating overly-tight spots, which could drastically accelerate the wear of the chain potentially leading to failure.