We recommend that you replace the entire set, which will provide you with trouble-free operation for the entire period of durability. If the apartment is really old, e.g. from the beginning of the 20th century, it is possible that the new door will not fit in the existing doorframe. On the contrary, in panel buildings, the standardized dimensions of doorframes were already used so it would be possible to use the old doorframe. However, it is necessary to carefully measure everything to avoid disappointment. The ideal solution is to replace the door and doorframe together. In this way you will get a perfectly functional set which is balanced with regard to aesthetics too. In any case we recommend the use of specialized services of installation companies for the installation of any new doorframes.