But if you intended a more common phrase like (steadfastness in continuing through hardship), here is the corrected proper form:
However, based on the transliteration "lbt alastmar fy alshdt" , it seems you likely meant: lbt alastmar fy alshdt
If you clarify the intended meaning, I can refine it further. For now, the most direct correction of your transliteration into proper Arabic script is: But if you intended a more common phrase
Here is the proper Arabic text for the phrase you provided: lbt alastmar fy alshdt
(Al-battu fī al-istimrār fī al-shiddah) — "Decisiveness in continuing through hardship."