My body weight like bitcoin-one step forward two steps back

One of my goals for this year is to gain weight. something about 5 kg nothing drustic. it might seem awkward to some of you, but Im quite a thin woman and I would like to be just a little bit firmer...
so lately Ive started working out and pay more attention to what I eat... turns out it really not that simple.

I started out weighing 50 kg.
after the first week I gained almost 2 kg

but now im back to the 50 zone again...around 50.8.

I thought the graph of that is a little bit like the ups and downs of crypto in the last months...but if it really is like that so im deffinetely in a good direction...its quite healthy I believe that after a rise comes a little fall and so on because that is the healthiest and safe way is best for everyone...no drastic changes.