"If you put in the work to sharpen the steel, it will eventually turn into needles." Do you have a similar proverb in English?

Solution 1:

Martin Manser, The Facts on File Dictionary of Proverbs (2002) offers two English sayings that are somewhat similar to the OP's in their view of the value of persistence:

constant dropping wears away a stone It is often possible to achieve a major purpose—for example, persuading people or breaking down their resistance—by a series of small but persistent actions or remarks: ... The proverb was first recorded in the 13th century, with different wording, but the sentiment it expresses is of ancient origin. Tibullus (c. 48–19 B.C.) "longa dies molli saxa peredit aqua {length of time eats away stones with soft water}."

and:

little strokes fell great oaks Great things can be achieved in small stages, or with persistent effort: ...The proverb is probably of ancient origin; in his Adagia (1500) the Dutch humanist Desiderius Erasmus quotes the Latinproverb "Multis ictibus deiicitur quercus {The oak is felled by many blows}."It also occurs in Shakespeare's play Henry VI, Part 3 (2:1): "And many strokes, though with a little axe,/Hews down and fells the hardest-timber'd oak."

The saying "Practice makes perfect" applies to persistence in developing mastery of some skill or task—which fits the situation of painstakingly gaining command of English—but it doesn't focus on persistence in working away at a task that is dauntingly large or otherwise difficult, and that doesn't show any meaningful progress after a even a fairly protracted amount of time dedicated to the task, as in the instance of sharpening steel into needles. For that scenario, I think, the two proverbs quoted in my answer are more suitable.