je suis en forme: I am fit, I feel great
J'espère que tu es en bonne forme means "I hope that you are in good shape" in English.
en forme -- healthy, in shape
En forme de coeur means 'heart-shaped' in French.
reste en forme
'fitness' may be translated by "mise en forme / remise en forme" ('un club de remise en forme = a fitness club) or "condition physique" (a fitness test) to be fit is "être en forme" or "être en bonne condition physique"
en pleine forme means 'completely fit', 'in great shape' in French.
en forme
en pleine forme
Depend the context: "en forme de..", "de forme...", "formé", "profilé". "En forme de triangle" (triangle-shaped), "De forme bizarre" (odd shaped), "bien formé" (well-shaped)
in English
Plate-forme nord means "North/northern platform" in English.
in