The reply to this question is two-fold.
On the one hand, you must consider that the CV you have to create in the platform must be in English. It is important to write it in a good standard of English as the evaluation of your profile will be based on this information. Therefore, if you do not speak English, we suggest you seek for help.
On the other hand, the knowledge of English, or another foreign language, is not compulsory to participate in the project, nor is it always essential to obtain a work abroad. The importance of the language depends on the professional field. For some kind of jobs, an high level in a specific language is requested, while in other cases technical skills are more relevant.
However, in our experience, language knowledge is very often a requirement of a job vacancy, and in some countries, such as Germany, it is almost always compulsory.
Considering the relevance of language knowledge in professional mobility processes, EURES TMS provides specific support: covering part of the costs of language training courses for pre-selected or selected candidates and offering financial support to SMEs organizing language training for newly hired staff.