die Kugel
bullet
A projectile fired from a gun.
Die Kugel traf die Zielscheibe genau in der Mitte.
The bullet hit the target right in the middle.

bullet / scoop / sphere
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bullet
A projectile fired from a gun.
Die Kugel traf die Zielscheibe genau in der Mitte.
The bullet hit the target right in the middle.

Since 'Kugel' has many meanings, context is crucial. Verbs like 'abfeuern' (to fire) or 'treffen' (to hit) point to a projectile (m01). Words like 'Eis' (ice cream), 'lecker' (delicious), or 'bestellen' (to order) refer to ice cream (m02). The sports context becomes clear through the verb 'stoßen' (to put/push) (m04).
Er bestellte drei Kugeln Eis mit Sahne.
He ordered three scoops of ice cream with whipped cream.
When ordering ice cream, 'Kugel' (scoop) is often combined with the flavor. For example, you say 'eine Kugel Schokolade' (one scoop of chocolate) or 'zwei Kugeln Vanille' (two scoops of vanilla).
Ich nehme eine Kugel Zitrone und eine Kugel Erdbeere, bitte.
I'll have one scoop of lemon and one scoop of strawberry, please.
In connection with firearms, typical phrases are 'eine Kugel abfeuern' (to fire a bullet), 'von einer Kugel getroffen werden' (to be hit by a bullet), or that a bullet is 'im Lauf steckt' (stuck in the barrel).
Der Polizist feuerte eine Kugel in die Luft.
The police officer fired a bullet into the air.
The idiom 'eine ruhige Kugel schieben' is a fixed unit. It means that someone has a very relaxed job or does not have to make much effort. The verb 'schieben' (to push) is not meant literally here.
Im neuen Job kann er endlich eine ruhige Kugel schieben.
In the new job, he can finally take it easy.
In athletics, 'die Kugel' (the shot) is used almost exclusively with the verb 'stoßen' (to put/push). The sport is called 'das Kugelstoßen' (shot put).
Die Athletin bereitet sich darauf vor, die Kugel zu stoßen.
The athlete is preparing to put the shot.
circle / district
'der Kreis' and 'die Kugel' are easy to confuse because both have to do with a round shape. The important difference is: a 'Kreis' is flat, so two-dimensional, for example on paper. A 'Kugel' is spatial, so three-dimensional, like a ball. If you draw something, it is usually a Kreis. If you can touch or roll something round, it is often a Kugel.

Elif hält eine kleine Kugel aus Holz in der Hand.
Elif is holding a small wooden sphere in her hand.
Frau Wolf zeichnet einen Kreis an die Tafel, damit die Form klarer wird.
Ms. Wolf draws a circle on the board so that the shape becomes clearer.