sql - Complexity in querying for data of two tables with a 'many to many relationship' creates time delay -

i have 'many many relationship' between 2 tables in database. 1 called "tools" other "groups". problem when want, example, tool names associated collection of groups, , return user in order present in list or something, action takes couple of seconds, , creates bad user experience. ideas of how can reduce time takes data fetched?

my linq:

    var tools = new hashset<string>();     //the groups user associated     foreach (var usergroup in usergroups)     {         //all groups in database         foreach (var group in context.groups)         {             if(group.groupname == usergroup)                 group.tools.foreach(t=>{                  tools.add(t.toolname);                 });         }     }     return tools;