das Selbstbewusstsein
self-confidence
Trust in one's own abilities, strengths, and worth; confidence.
Sie trat mit großem Selbstbewusstsein auf und überzeugte das Publikum.
She appeared with great self-confidence and convinced the audience.

self-confidence / self-awareness
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self-confidence
Trust in one's own abilities, strengths, and worth; confidence.
Sie trat mit großem Selbstbewusstsein auf und überzeugte das Publikum.
She appeared with great self-confidence and convinced the audience.

The word is made up of 'selbst' (self), 'bewusst' (aware/conscious), and the ending '-sein' (being). It literally means being aware of oneself. This structure helps you understand both meanings: self-confidence and self-awareness.
Durch den Erfolgserlebnis wuchs sein Selbstbewusstsein.
Because of the experience of success, his self-confidence grew.
In everyday language, the meaning 'Selbstvertrauen' (self-confidence) is almost always meant. The philosophical meaning 'Selbstwahrnehmung' (self-awareness) is found mainly in academic or psychological texts.
Er hat nicht genug Selbstbewusstsein, um vor vielen Menschen zu sprechen.
He doesn't have enough self-confidence to speak in front of many people.
For the meaning 'Selbstvertrauen' (self-confidence), combinations with adjectives such as 'groß' (great), 'stark' (strong), or 'wenig' (little) are typical. Common verbs are 'haben' (to have), 'stärken' (to strengthen), 'aufbauen' (to build up), or 'zeigen' (to show).
Man kann lernen, sein Selbstbewusstsein zu stärken.
You can learn to strengthen your self-confidence.
consciousness / awareness
'Bewusstsein' and 'Selbstbewusstsein' are closely related because both can have to do with perception and knowledge about oneself. 'Bewusstsein' generally means that you are awake, think, feel, and perceive your surroundings. It can also mean that you understand an issue, for example 'Umweltbewusstsein' (environmental awareness). In everyday language, 'Selbstbewusstsein' usually means confidence in yourself. In a philosophical sense, it can also mean awareness of oneself as a person. Learners can easily confuse the words because 'Selbstbewusstsein' contains the word 'Bewusstsein'. For everyday use, the important point is: someone who has no 'Bewusstsein' is not fully aware; someone who has 'Selbstbewusstsein' comes across as confident.

Durch den Sprachkurs hat Lena mehr Selbstbewusstsein bekommen.
Through the language course, Lena gained more self-confidence.
Nach dem Unfall verlor der Radfahrer kurz das Bewusstsein.
After the accident, the cyclist briefly lost consciousness.