I need to say that some problems are appearing on the project, for that I wanted to say
bottlenecks are emerging.
Is this term correct? If not, how can I say a similar formal sentence?
Users of metaphor must always beware of mischievous literalists (like me) who see the funny side of what is known as a 'mixed metaphor'. Metaphor, when appropriately used, can make a point more vivid and memorable. Mixed metaphors have the opposite effect.
A combination of two or more incompatible metaphors. [https://en.oxforddictionaries.com/definition/mixed_metaphor]
The business is run by C J, a powerful figure full of impressive-sounding aphorisms that, on analysis, prove meaningless, comprising a heap of mixed metaphors and clichés piled one on top of another.
Your example is not as bad as the example, but it is vulnerable to an unintended amusement. A bottleneck, taken literally, means what it does from the way in which the neck of a bottle slows the flow of a liquid. The French call it a cork (bouchon). You follow this three-dimensional image with the two-dimensional metaphor of a one-dimensional "surface".
However, this has nothing to do with correct or incorrect use. Metaphors can be apt or inept, but not correct or incorrect. They are a matter of style or taste. The term mixed metaphor is a derogatory expression, which applies to bad style. Style is a matter of taste. And, in the words of the Roman poet, Horace, in his poem De Arte Poetica (On the Art of poetry/literature:-
de gustibus non est / disputandum.
One should not argue about taste.
I personally would smile inwardly, but most people would hardly notice if they noticed at all.