The Image A is of - Ailanthus probably and the image H is Acer Species probably, I will be very happy if my assumption is correct. herewith I also requiest you to do not collect such incomplete specimen without flower and fruit which is not identifiable.
@Lukas Petrulaitis, @Sunit Mitra thank you very much for the scientific name of the trees. Are very useful for me. I think also that A is Ailanthus altissima and C is Fraxinus.
A: I am quite sure that this is not Ailanthus altissima. Neither shape of the base of the leaflets nor their serrate margin fit for this species. E seems to be the same species.
B: Koelreuteria paniculata (Sapindaceae)
C/D: Some Fraxinus, most likely Fraxinus pennsylvanica.
"By their fruits ye shall know them", as my Botany Professor used to say. Do these leaves have a rank smell? Reproductive structures are the best way to positively ID a tree or plant.
In my opinion, A and E are Juglans nigra. The leaves are missing the terminal leaflets, which is normal in J. nigra. Also the serrate margin fits well.
"By their fruits ye shall know them." Examining plant specimens with reproductive structures are the best way to identify plants to their respective specific epithet.
It is not easy to identify only with pictures of leaves, it was important other featureslike flowers, fruits, an overall picture of the plant and the location.
The images, I think
A - Juglandaceae Family ?.
B -Koelreuteria paniculata?
C -Fraxinus sp.
D -Fraxinus sp
And -Family Juglandaceae.?,
F - Platanaceae family. Probably Platanus orientalis?
Approach the Botanical survey center existing in your country with the different parts of the plants. Refer International Plant Research Centers Directory too
It is not that easy identifying trees from leaves alone, particularly if you do not show how the leaves are attached to the stems. The identifications above are mere guesses, but these are plants frequently found planted (and naturalised) in Bucharest.
Confirming Koelreuteria paniculata for B (unmistakeable at least among temperate zone trees - the leaflets look like they are falling apart), Platanus for F and Acer negundo for H.
One would need additional details like floral structure, fruit and bark characteristics, and an appropriate family key in order to determine the exact identity of the trees.