What happens to the phase spectrum when I resample?
1- Is this resampling correct?

No. Resampling is almost never 100% correct but it usually requires a complicated trade off between different artifacts and properties: passband extension and flatness, stop-band attenuation and size, aliasing rejection, phase distortion, onset &amp; transient preservation, causality, CPU and memory requirements etc.
Which trade off is the best, depends a lot on the requirements of your specific application.

2- Is there a solution to create any kind of corresponding phase information for higher frequencies?

Why would you need that? Your original signal cannot contain any energy at frequencies equal or above the original Nyquist frequency. When you re-sample you extend the frequency range, but the energy at these new frequencies (between 11 MHz and 20 MHz) is close to or exactly zero. That's the whole point of a &quot;good&quot; interpolation: make sure you don't add stuff that wasn't there before.
That means the phase at the new frequencies is either undefined or doesn't really matter since there is no relevant energy. If the magnitude is zero, it doesn't matter what the phase is.