This is my translation from the last words of the 3rd line to about a third of the 5th line.
mentioned - mentioned
dicti - to say, speak, utter, tell, mention, relate, affirm, declare, state, assert
quous - if any, It could also be short for the word 'quousque',:- until what time, till when, how long; or (quo usque) [how long? how far?].
Lancelot Armstrong - Lancelot Armstrong
durank?
sua - his, their, their own, his own, it's.
bita? -
possess - possess
fuerunt - were, have been, they were, there were, been.
per - before, aforesaid,
prefatum - the said
Francis Armstrong - Francis Armstrong
erus? looks like opus? - Master of a House, Proprietor, Master of a Family, Owner, Lord (Laird?), Sweetheart, God.
nepotem - grandson, the grandson of, nephew, the nephew of
semper - always, eternally, ever, perpetually, fore ever,
ab - from the, by the.
erus? looks like opus? - Master of a House, Proprietor, Master of a Family, Owner, Lord (Laird?), Sweetheart, God.
decessu - departure, decease of, decease,
tanquam - as much as, so as, just as, like as, as if, so to speak
hereditary properties - hereditary properties
earundem? - the same, same, their, of their.
possess - possess
sunt? - to be, exist, live
sicuti - as, as he, as it, just as.
etiam - also, is also, also the.
pre - aforesaid

??
dicti - to say, speak, utter, tell, mention, relate, affirm, declare, state, assert
quous - if any, It could also be short for the word 'quousque', :- until what time, till when, how long; or (quo usque) [how long? how far?].
Lancloti - Lancelot
hereditary property - hereditary property
et - and, and his,
possessors - possessors
dictarum - of the said, said, aforesaid, the aforesaid.
terrarum - of the lands.