I did my first brew from a 5 litres blonde beer kit. I wanted to bottle it after 2 weeks (according to the recipe ) but I got scared about over carbonation so I decided to leave it another week in the carboy. Now, 5 days later, after I moved the carboy when I wanted to bottle my beer, I see a lot of fizzing going arround. Before it was dormant and now it seem active again with a tiny amount of foam on top. Does it mean it got in another stage of fermentation? Now I am even more scared about over carbonation. And by the way, I didn't get a hydrometer nor a refractometer in the kit so I am in the unknown here. I would appreciate any thoughts, Adrian.
The release of gas when you moved it is not uncommon. There is usually residual CO2 from the fermentation dissolved in the liquid and by agitating the liquid when you moved it, some of that gas is escaping. Much like swirling a glass of beer to get more foam or aroma out of it. (For the record, up swings in temperature can also generate the appearance of bubbles too.)
I'd say go to bottle as normal if you think you are ready. Three weeks is probably more than enough if fermentation went well. When you rack the brew over to bottle taste a sample. If it tastes fine then I wouldn't be too concerned that the activity your seeing is something else like a microbial contaminant.
Lastly... get a hydrometer for the future.
Measure gravity. That's the only way to be sure.
You can have little to no bubbles and fermentation going on if the lid didn't seal completely. Or you can have bubbles and no fermentation if you release residual CO2. Or you can have stuck fermentation you will unstuck by agitating and adding priming sugar. So don't guess it. Measure it. Three days without gravity change should be perfect.