Con el tiempo, me siento más seguro cuando hablo en español.

Yes, literally it is with the time, but as an expression it means over time, as time goes by, or in time.

In Spanish, con el tiempo is a very common fixed phrase:

• Con el tiempo, todo mejora.
• Con el tiempo, lo entenderás.

So in your sentence, it sets the time frame: this is something that happens gradually.

Because sentirse means to feel in the sense of to feel oneself / to feel a certain way.

• siento = I feel something
  
  • Siento frío = I feel cold
  • Siento miedo = I feel fear
• me siento = I feel
  • adjective/state
    
    • Me siento cansado = I feel tired
    • Me siento seguro = I feel confident / I feel sure of myself

So here, me is necessary because the structure is sentirse + adjective.

Yes, seguro can mean several related things depending on context:

• safe
• sure/certain
• confident

In me siento más seguro, it means I feel more confident or more self-assured.

This is very natural Spanish. It does not usually mean physically safe here. The context of speaking a language makes the meaning confident.

Because the sentence is talking about becoming more confident, not about becoming better in a general sense.

• más seguro = more confident
• mejor = better

Compare:

• Con el tiempo, hablo mejor en español. = Over time, I speak Spanish better.
• Con el tiempo, me siento más seguro cuando hablo en español. = Over time, I feel more confident when I speak in Spanish.

Both are correct, but they express different ideas:

• mejor focuses on skill/performance
• más seguro focuses on confidence

Because Spanish often uses the present tense for repeated, habitual, or general situations.

Here, cuando hablo en español means:

• when I speak in Spanish
• when I’m speaking Spanish
• whenever I speak Spanish

It is not referring to one single past event. It describes a general pattern: every time or in situations where the speaker speaks Spanish.

Both can exist, but they are not exactly the same in nuance.

• hablar español = to speak Spanish as a language ability
• hablar en español = to speak in Spanish, focusing on the language being used in that moment

In your sentence, cuando hablo en español emphasizes the situation of speaking in the Spanish language.

Compare:

• Hablo español. = I speak Spanish.
• Te lo digo en español. = I’m telling you it in Spanish.

So en español is very natural here because it refers to the context in which the speaker feels more confident.

Yes, you might hear that, and many people would understand it, but cuando hablo en español sounds more clearly like when I am speaking in Spanish.

A useful distinction is:

• hablar español = to know/speak the language
• hablar en español = to speak using Spanish in a particular situation

So in this sentence, en español is slightly more precise and idiomatic for the intended meaning.

Because Spanish often leaves out subject pronouns when they are already clear from the verb form.

• me siento already tells you it means I feel
• hablo already tells you it means I speak

So:

• Con el tiempo, me siento más seguro cuando hablo en español.

is more natural than:

• Con el tiempo, yo me siento más seguro cuando yo hablo en español.

You can add yo for emphasis, contrast, or clarity, but it is not normally needed.

The adjective must agree with the gender of the speaker.

• A male speaker would usually say seguro
• A female speaker would usually say segura

So:

• Me siento más seguro = said by a man
• Me siento más segura = said by a woman

If you are learning the sentence for your own use, choose the form that matches you.

Yes. Spanish allows some flexibility in word order.

All of these are possible:

• Con el tiempo, me siento más seguro cuando hablo en español.
• Me siento más seguro con el tiempo cuando hablo en español.
• Me siento más seguro cuando hablo en español con el tiempo.

But the first version sounds the most natural because con el tiempo works well as an opening phrase that frames the whole statement.

Sometimes, but the meaning changes slightly.

• me siento más seguro = I feel more confident
• estoy más seguro = I am more sure / more certain, often about something specific

If you are talking about your emotional state or confidence level, me siento más seguro is the best choice.

Examples:

• Me siento más seguro al hablar en español. = I feel more confident speaking Spanish.
• Estoy más seguro de mi respuesta. = I’m more sure about my answer.

So for this sentence, me siento is the more natural verb.